Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $237.52   5.132%   $249.7095   $249.71   $249.70   $249.70  
  Purchase #2 $218.87   4.466%   $228.6447   $228.64   $228.65   $228.60  
  Purchase #3 $216.83   12.487%   $243.9056   $243.91   $243.90   $243.90  
  Purchase #4 $157.82   11.715%   $176.3086   $176.31   $176.30   $176.30  
  Purchase #5 $222.64   5.459%   $234.7939   $234.79   $234.80   $234.80  
  Purchase #6 $198.97   10.275%   $219.4142   $219.41   $219.40   $219.40  
  Purchase #7 $209.82   4.765%   $219.8179   $219.82   $219.80   $219.80  
  7 purchase totals = $1,462.47       $1,572.5944   $1,572.59   $1,572.55   $1,572.50