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 $62.29   10.293%   $68.7015   $68.70   $68.70   $68.70  
  Purchase #2 $85.82   6.792%   $91.6489   $91.65   $91.65   $91.60  
  Purchase #3 $151.53   9.708%   $166.2405   $166.24   $166.25   $166.20  
  Purchase #4 $206.54   6.771%   $220.5248   $220.52   $220.50   $220.50  
  Purchase #5 $179.79   11.850%   $201.0951   $201.10   $201.10   $201.10  
  Purchase #6 $150.62   10.622%   $166.6189   $166.62   $166.60   $166.60  
  Purchase #7 $159.85   13.207%   $180.9614   $180.96   $180.95   $181.00  
  7 purchase totals = $996.44       $1,095.7911   $1,095.79   $1,095.75   $1,095.70