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 $56.85   9.227%   $62.0955   $62.10   $62.10   $62.10  
  Purchase #2 $244.40   11.131%   $271.6042   $271.60   $271.60   $271.60  
  Purchase #3 $219.76   10.493%   $242.8194   $242.82   $242.80   $242.80  
  Purchase #4 $44.79   9.369%   $48.9864   $48.99   $49.00   $49.00  
  Purchase #5 $232.76   4.118%   $242.3451   $242.35   $242.35   $242.30  
  Purchase #6 $226.77   11.115%   $251.9755   $251.98   $252.00   $252.00  
  Purchase #7 $10.40   12.688%   $11.7196   $11.72   $11.70   $11.70  
  7 purchase totals = $1,035.73       $1,131.5457   $1,131.56   $1,131.55   $1,131.50