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 $212.68   8.178%   $230.073   $230.07   $230.05   $230.10  
  Purchase #2 $221.84   6.832%   $236.9961   $237.00   $237.00   $237.00  
  Purchase #3 $81.69   8.860%   $88.9277   $88.93   $88.95   $88.90  
  Purchase #4 $140.72   6.841%   $150.3467   $150.35   $150.35   $150.30  
  Purchase #5 $182.25   6.400%   $193.914   $193.91   $193.90   $193.90  
  Purchase #6 $95.68   12.488%   $107.6285   $107.63   $107.65   $107.60  
  Purchase #7 $156.42   4.187%   $162.9693   $162.97   $162.95   $163.00  
  7 purchase totals = $1,091.28       $1,170.8553   $1,170.86   $1,170.85   $1,170.80