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 $55.82   12.160%   $62.6077   $62.61   $62.60   $62.60  
  Purchase #2 $150.36   12.488%   $169.137   $169.14   $169.15   $169.10  
  Purchase #3 $222.88   9.203%   $243.3916   $243.39   $243.40   $243.40  
  Purchase #4 $120.27   7.496%   $129.2854   $129.29   $129.30   $129.30  
  Purchase #5 $209.98   7.301%   $225.3106   $225.31   $225.30   $225.30  
  Purchase #6 $162.47   8.713%   $176.626   $176.63   $176.65   $176.60  
  Purchase #7 $184.33   9.577%   $201.9833   $201.98   $202.00   $202.00  
  7 purchase totals = $1,106.11       $1,208.3416   $1,208.35   $1,208.40   $1,208.30