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 $232.59   5.192%   $244.6661   $244.67   $244.65   $244.70  
  Purchase #2 $205.39   10.314%   $226.5739   $226.57   $226.55   $226.60  
  Purchase #3 $45.79   7.685%   $49.309   $49.31   $49.30   $49.30  
  Purchase #4 $206.89   3.262%   $213.6388   $213.64   $213.65   $213.60  
  Purchase #5 $34.51   3.709%   $35.79   $35.79   $35.80   $35.80  
  Purchase #6 $227.93   3.257%   $235.3537   $235.35   $235.35   $235.40  
  Purchase #7 $59.28   6.255%   $62.988   $62.99   $63.00   $63.00  
  7 purchase totals = $1,012.38       $1,068.3195   $1,068.32   $1,068.30   $1,068.40