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 $54.60   13.251%   $61.835   $61.84   $61.85   $61.80  
  Purchase #2 $89.37   13.266%   $101.2258   $101.23   $101.25   $101.20  
  Purchase #3 $150.36   10.471%   $166.1042   $166.10   $166.10   $166.10  
  Purchase #4 $202.89   4.368%   $211.7522   $211.75   $211.75   $211.80  
  Purchase #5 $178.75   7.256%   $191.7201   $191.72   $191.70   $191.70  
  Purchase #6 $158.99   5.506%   $167.744   $167.74   $167.75   $167.70  
  Purchase #7 $240.59   5.534%   $253.9043   $253.90   $253.90   $253.90  
  7 purchase totals = $1,075.55       $1,154.2856   $1,154.28   $1,154.30   $1,154.20