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 $91.64   4.783%   $96.0231   $96.02   $96.00   $96.00  
  Purchase #2 $156.31   8.462%   $169.537   $169.54   $169.55   $169.50  
  Purchase #3 $249.74   5.198%   $262.7215   $262.72   $262.70   $262.70  
  Purchase #4 $171.55   12.381%   $192.7896   $192.79   $192.80   $192.80  
  Purchase #5 $185.52   10.674%   $205.3224   $205.32   $205.30   $205.30  
  Purchase #6 $162.63   10.813%   $180.2152   $180.22   $180.20   $180.20  
  Purchase #7 $51.41   8.424%   $55.7408   $55.74   $55.75   $55.70  
  7 purchase totals = $1,068.80       $1,162.3496   $1,162.35   $1,162.30   $1,162.20