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 $214.74   4.643%   $224.7104   $224.71   $224.70   $224.70  
  Purchase #2 $224.98   8.167%   $243.3541   $243.35   $243.35   $243.40  
  Purchase #3 $51.96   9.739%   $57.0204   $57.02   $57.00   $57.00  
  Purchase #4 $128.77   9.556%   $141.0753   $141.08   $141.10   $141.10  
  Purchase #5 $193.57   4.655%   $202.5807   $202.58   $202.60   $202.60  
  Purchase #6 $117.76   11.729%   $131.5721   $131.57   $131.55   $131.60  
  Purchase #7 $142.51   7.695%   $153.4761   $153.48   $153.50   $153.50  
  7 purchase totals = $1,074.29       $1,153.7891   $1,153.79   $1,153.80   $1,153.90