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 $116.34   8.374%   $126.0823   $126.08   $126.10   $126.10  
  Purchase #2 $153.67   13.613%   $174.5891   $174.59   $174.60   $174.60  
  Purchase #3 $48.57   3.614%   $50.3253   $50.33   $50.35   $50.30  
  Purchase #4 $243.30   11.649%   $271.642   $271.64   $271.65   $271.60  
  Purchase #5 $138.62   5.514%   $146.2635   $146.26   $146.25   $146.30  
  Purchase #6 $170.29   13.492%   $193.2655   $193.27   $193.25   $193.30  
  Purchase #7 $238.78   3.188%   $246.3923   $246.39   $246.40   $246.40  
  7 purchase totals = $1,109.57       $1,208.5600   $1,208.56   $1,208.60   $1,208.60