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 $104.27   9.464%   $114.1381   $114.14   $114.15   $114.10  
  Purchase #2 $70.53   5.390%   $74.3316   $74.33   $74.35   $74.30  
  Purchase #3 $154.36   7.425%   $165.8212   $165.82   $165.80   $165.80  
  Purchase #4 $93.67   6.308%   $99.5787   $99.58   $99.60   $99.60  
  Purchase #5 $87.26   11.351%   $97.1649   $97.16   $97.15   $97.20  
  Purchase #6 $204.81   12.816%   $231.0584   $231.06   $231.05   $231.10  
  Purchase #7 $211.45   8.289%   $228.9771   $228.98   $229.00   $229.00  
  7 purchase totals = $926.35       $1,011.0700   $1,011.07   $1,011.10   $1,011.10