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 $117.94   6.871%   $126.0437   $126.04   $126.05   $126.00  
  Purchase #2 $173.37   6.342%   $184.3651   $184.37   $184.35   $184.40  
  Purchase #3 $55.54   10.164%   $61.1851   $61.19   $61.20   $61.20  
  Purchase #4 $38.55   3.365%   $39.8472   $39.85   $39.85   $39.80  
  Purchase #5 $146.35   6.488%   $155.8452   $155.85   $155.85   $155.80  
  Purchase #6 $212.32   6.581%   $226.2928   $226.29   $226.30   $226.30  
  Purchase #7 $165.90   4.515%   $173.3904   $173.39   $173.40   $173.40  
  7 purchase totals = $909.97       $966.9695   $966.98   $967.00   $966.90