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 $53.39   6.528%   $56.8753   $56.88   $56.90   $56.90  
  Purchase #2 $99.45   4.645%   $104.0695   $104.07   $104.05   $104.10  
  Purchase #3 $167.94   10.823%   $186.1161   $186.12   $186.10   $186.10  
  Purchase #4 $166.30   4.314%   $173.4742   $173.47   $173.45   $173.50  
  Purchase #5 $9.35   13.766%   $10.6371   $10.64   $10.65   $10.60  
  Purchase #6 $244.35   7.643%   $263.0257   $263.03   $263.05   $263.00  
  Purchase #7 $200.89   9.734%   $220.4446   $220.44   $220.45   $220.40  
  7 purchase totals = $941.67       $1,014.6425   $1,014.65   $1,014.65   $1,014.60