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 $224.66   7.264%   $240.9793   $240.98   $241.00   $241.00  
  Purchase #2 $98.78   3.307%   $102.0467   $102.05   $102.05   $102.00  
  Purchase #3 $221.73   7.694%   $238.7899   $238.79   $238.80   $238.80  
  Purchase #4 $196.33   12.451%   $220.775   $220.78   $220.80   $220.80  
  Purchase #5 $156.30   9.593%   $171.2939   $171.29   $171.30   $171.30  
  Purchase #6 $87.78   7.682%   $94.5233   $94.52   $94.50   $94.50  
  Purchase #7 $115.98   9.253%   $126.7116   $126.71   $126.70   $126.70  
  7 purchase totals = $1,101.56       $1,195.1197   $1,195.12   $1,195.15   $1,195.10