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 $203.84   4.690%   $213.4001   $213.40   $213.40   $213.40  
  Purchase #2 $31.39   6.333%   $33.3779   $33.38   $33.40   $33.40  
  Purchase #3 $99.74   6.482%   $106.2051   $106.21   $106.20   $106.20  
  Purchase #4 $155.80   8.474%   $169.0025   $169.00   $169.00   $169.00  
  Purchase #5 $31.79   8.693%   $34.5535   $34.55   $34.55   $34.60  
  Purchase #6 $184.48   11.573%   $205.8299   $205.83   $205.85   $205.80  
  Purchase #7 $188.92   7.222%   $202.5638   $202.56   $202.55   $202.60  
  7 purchase totals = $895.96       $964.9328   $964.93   $964.95   $965.00