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 $43.60   5.557%   $46.0229   $46.02   $46.00   $46.00  
  Purchase #2 $80.92   5.420%   $85.3059   $85.31   $85.30   $85.30  
  Purchase #3 $208.46   4.644%   $218.1409   $218.14   $218.15   $218.10  
  Purchase #4 $149.87   11.628%   $167.2969   $167.30   $167.30   $167.30  
  Purchase #5 $111.40   9.408%   $121.8805   $121.88   $121.90   $121.90  
  Purchase #6 $41.37   6.564%   $44.0855   $44.09   $44.10   $44.10  
  Purchase #7 $212.35   9.537%   $232.6018   $232.60   $232.60   $232.60  
  7 purchase totals = $847.97       $915.3344   $915.34   $915.35   $915.30