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 $119.94   5.612%   $126.671   $126.67   $126.65   $126.70  
  Purchase #2 $174.46   5.481%   $184.0222   $184.02   $184.00   $184.00  
  Purchase #3 $162.95   7.173%   $174.6384   $174.64   $174.65   $174.60  
  Purchase #4 $30.77   11.529%   $34.3175   $34.32   $34.30   $34.30  
  Purchase #5 $215.61   5.628%   $227.7445   $227.74   $227.75   $227.70  
  Purchase #6 $217.85   13.620%   $247.5212   $247.52   $247.50   $247.50  
  Purchase #7 $115.85   12.591%   $130.4367   $130.44   $130.45   $130.40  
  7 purchase totals = $1,037.43       $1,125.3515   $1,125.35   $1,125.30   $1,125.20