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 $194.85   4.646%   $203.9027   $203.90   $203.90   $203.90  
  Purchase #2 $80.98   3.548%   $83.8532   $83.85   $83.85   $83.90  
  Purchase #3 $99.51   5.621%   $105.1035   $105.10   $105.10   $105.10  
  Purchase #4 $73.26   3.249%   $75.6402   $75.64   $75.65   $75.60  
  Purchase #5 $108.43   5.363%   $114.2451   $114.25   $114.25   $114.20  
  Purchase #6 $197.83   3.406%   $204.5681   $204.57   $204.55   $204.60  
  Purchase #7 $198.28   13.797%   $225.6367   $225.64   $225.65   $225.60  
  7 purchase totals = $953.14       $1,012.9495   $1,012.95   $1,012.95   $1,012.90