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 $241.29   7.399%   $259.143   $259.14   $259.15   $259.10  
  Purchase #2 $58.98   7.121%   $63.18   $63.18   $63.20   $63.20  
  Purchase #3 $217.39   6.705%   $231.966   $231.97   $231.95   $232.00  
  Purchase #4 $234.89   4.268%   $244.9151   $244.92   $244.90   $244.90  
  Purchase #5 $216.44   11.573%   $241.4886   $241.49   $241.50   $241.50  
  Purchase #6 $80.52   11.823%   $90.0399   $90.04   $90.05   $90.00  
  Purchase #7 $224.90   8.793%   $244.6755   $244.68   $244.70   $244.70  
  7 purchase totals = $1,274.41       $1,375.4081   $1,375.42   $1,375.45   $1,375.40