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 $168.43   10.754%   $186.543   $186.54   $186.55   $186.50  
  Purchase #2 $88.66   3.459%   $91.7267   $91.73   $91.75   $91.70  
  Purchase #3 $205.37   13.771%   $233.6515   $233.65   $233.65   $233.70  
  Purchase #4 $90.93   6.503%   $96.8432   $96.84   $96.85   $96.80  
  Purchase #5 $235.52   3.592%   $243.9799   $243.98   $244.00   $244.00  
  Purchase #6 $106.35   10.109%   $117.1009   $117.10   $117.10   $117.10  
  Purchase #7 $190.33   12.521%   $214.1612   $214.16   $214.15   $214.20  
  7 purchase totals = $1,085.59       $1,184.0064   $1,184.00   $1,184.05   $1,184.00