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 $203.98   3.565%   $211.2519   $211.25   $211.25   $211.30  
  Purchase #2 $226.43   4.818%   $237.3394   $237.34   $237.35   $237.30  
  Purchase #3 $68.25   9.516%   $74.7447   $74.74   $74.75   $74.70  
  Purchase #4 $26.59   10.265%   $29.3195   $29.32   $29.30   $29.30  
  Purchase #5 $249.99   4.245%   $260.6021   $260.60   $260.60   $260.60  
  Purchase #6 $162.50   6.307%   $172.7489   $172.75   $172.75   $172.70  
  Purchase #7 $22.92   6.840%   $24.4877   $24.49   $24.50   $24.50  
  7 purchase totals = $960.66       $1,010.4942   $1,010.49   $1,010.50   $1,010.40