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 $43.46   6.271%   $46.1854   $46.19   $46.20   $46.20  
  Purchase #2 $245.27   3.675%   $254.2837   $254.28   $254.30   $254.30  
  Purchase #3 $116.29   8.534%   $126.2142   $126.21   $126.20   $126.20  
  Purchase #4 $163.73   6.457%   $174.302   $174.30   $174.30   $174.30  
  Purchase #5 $245.60   8.867%   $267.3774   $267.38   $267.40   $267.40  
  Purchase #6 $201.29   11.851%   $225.1449   $225.14   $225.15   $225.10  
  Purchase #7 $113.52   4.769%   $118.9338   $118.93   $118.95   $118.90  
  7 purchase totals = $1,129.16       $1,212.4414   $1,212.43   $1,212.50   $1,212.40