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 $41.36   12.264%   $46.4324   $46.43   $46.45   $46.40  
  Purchase #2 $92.55   12.860%   $104.4519   $104.45   $104.45   $104.50  
  Purchase #3 $220.71   9.413%   $241.4854   $241.49   $241.50   $241.50  
  Purchase #4 $237.31   10.795%   $262.9276   $262.93   $262.95   $262.90  
  Purchase #5 $19.45   3.426%   $20.1164   $20.12   $20.10   $20.10  
  Purchase #6 $225.80   5.164%   $237.4603   $237.46   $237.45   $237.50  
  Purchase #7 $167.96   8.265%   $181.8419   $181.84   $181.85   $181.80  
  7 purchase totals = $1,005.14       $1,094.7159   $1,094.72   $1,094.75   $1,094.70