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 $62.52   8.539%   $67.8586   $67.86   $67.85   $67.90  
  Purchase #2 $147.44   9.561%   $161.5367   $161.54   $161.55   $161.50  
  Purchase #3 $51.48   7.738%   $55.4635   $55.46   $55.45   $55.50  
  Purchase #4 $232.88   13.487%   $264.2885   $264.29   $264.30   $264.30  
  Purchase #5 $202.82   5.355%   $213.681   $213.68   $213.70   $213.70  
  Purchase #6 $200.94   9.131%   $219.2878   $219.29   $219.30   $219.30  
  Purchase #7 $207.31   8.364%   $224.6494   $224.65   $224.65   $224.60  
  7 purchase totals = $1,105.39       $1,206.7655   $1,206.77   $1,206.80   $1,206.80