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 $58.54   4.150%   $60.9694   $60.97   $60.95   $61.00  
  Purchase #2 $242.37   11.304%   $269.7675   $269.77   $269.75   $269.80  
  Purchase #3 $116.42   3.220%   $120.1687   $120.17   $120.15   $120.20  
  Purchase #4 $213.32   8.720%   $231.9215   $231.92   $231.90   $231.90  
  Purchase #5 $75.92   10.604%   $83.9706   $83.97   $83.95   $84.00  
  Purchase #6 $215.43   3.772%   $223.556   $223.56   $223.55   $223.60  
  Purchase #7 $110.81   6.740%   $118.2786   $118.28   $118.30   $118.30  
  7 purchase totals = $1,032.81       $1,108.6323   $1,108.64   $1,108.55   $1,108.80