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 $117.76   4.675%   $123.2653   $123.27   $123.25   $123.30  
  Purchase #2 $211.31   8.246%   $228.7346   $228.73   $228.75   $228.70  
  Purchase #3 $194.91   6.121%   $206.8404   $206.84   $206.85   $206.80  
  Purchase #4 $75.85   11.594%   $84.644   $84.64   $84.65   $84.60  
  Purchase #5 $123.69   7.860%   $133.412   $133.41   $133.40   $133.40  
  Purchase #6 $183.59   5.702%   $194.0583   $194.06   $194.05   $194.10  
  Purchase #7 $212.74   5.344%   $224.1088   $224.11   $224.10   $224.10  
  7 purchase totals = $1,119.85       $1,195.0634   $1,195.06   $1,195.05   $1,195.00