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 $94.46   7.462%   $101.5086   $101.51   $101.50   $101.50  
  Purchase #2 $188.57   9.752%   $206.9593   $206.96   $206.95   $207.00  
  Purchase #3 $202.84   6.214%   $215.4445   $215.44   $215.45   $215.40  
  Purchase #4 $124.48   11.811%   $139.1823   $139.18   $139.20   $139.20  
  Purchase #5 $168.31   12.585%   $189.4918   $189.49   $189.50   $189.50  
  Purchase #6 $91.29   5.243%   $96.0763   $96.08   $96.10   $96.10  
  Purchase #7 $238.87   9.813%   $262.3103   $262.31   $262.30   $262.30  
  7 purchase totals = $1,108.82       $1,210.9731   $1,210.97   $1,211.00   $1,211.00