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 $41.75   10.239%   $46.0248   $46.02   $46.00   $46.00  
  Purchase #2 $225.53   4.448%   $235.5616   $235.56   $235.55   $235.60  
  Purchase #3 $45.73   10.155%   $50.3739   $50.37   $50.35   $50.40  
  Purchase #4 $203.72   7.783%   $219.5755   $219.58   $219.60   $219.60  
  Purchase #5 $67.36   11.117%   $74.8484   $74.85   $74.85   $74.80  
  Purchase #6 $233.49   8.461%   $253.2456   $253.25   $253.25   $253.20  
  Purchase #7 $126.99   3.782%   $131.7928   $131.79   $131.80   $131.80  
  7 purchase totals = $944.57       $1,011.4226   $1,011.42   $1,011.40   $1,011.40