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 $60.74   3.385%   $62.796   $62.80   $62.80   $62.80  
  Purchase #2 $146.74   13.700%   $166.8434   $166.84   $166.85   $166.80  
  Purchase #3 $147.73   12.365%   $165.9968   $166.00   $166.00   $166.00  
  Purchase #4 $86.89   7.463%   $93.3746   $93.37   $93.35   $93.40  
  Purchase #5 $59.35   4.295%   $61.8991   $61.90   $61.90   $61.90  
  Purchase #6 $216.37   11.439%   $241.1206   $241.12   $241.10   $241.10  
  Purchase #7 $148.92   5.134%   $156.5656   $156.57   $156.55   $156.60  
  7 purchase totals = $866.74       $948.5961   $948.60   $948.55   $948.60