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 $44.90   3.147%   $46.313   $46.31   $46.30   $46.30  
  Purchase #2 $140.39   6.584%   $149.6333   $149.63   $149.65   $149.60  
  Purchase #3 $50.67   5.254%   $53.3322   $53.33   $53.35   $53.30  
  Purchase #4 $190.43   4.144%   $198.3214   $198.32   $198.30   $198.30  
  Purchase #5 $167.55   4.701%   $175.4265   $175.43   $175.45   $175.40  
  Purchase #6 $138.80   5.202%   $146.0204   $146.02   $146.00   $146.00  
  Purchase #7 $243.31   8.360%   $263.6507   $263.65   $263.65   $263.70  
  7 purchase totals = $976.05       $1,032.6975   $1,032.69   $1,032.70   $1,032.60