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 $148.92   12.529%   $167.5782   $167.58   $167.60   $167.60  
  Purchase #2 $216.86   4.494%   $226.6057   $226.61   $226.60   $226.60  
  Purchase #3 $67.76   6.558%   $72.2037   $72.20   $72.20   $72.20  
  Purchase #4 $25.43   3.424%   $26.3007   $26.30   $26.30   $26.30  
  Purchase #5 $138.39   12.274%   $155.376   $155.38   $155.40   $155.40  
  Purchase #6 $63.36   4.740%   $66.3633   $66.36   $66.35   $66.40  
  Purchase #7 $41.91   13.815%   $47.6999   $47.70   $47.70   $47.70  
  7 purchase totals = $702.63       $762.1275   $762.13   $762.15   $762.20