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 $71.29   4.675%   $74.6228   $74.62   $74.60   $74.60  
  Purchase #2 $155.98   7.607%   $167.8454   $167.85   $167.85   $167.80  
  Purchase #3 $123.64   6.370%   $131.5159   $131.52   $131.50   $131.50  
  Purchase #4 $92.25   11.761%   $103.0995   $103.10   $103.10   $103.10  
  Purchase #5 $106.83   12.420%   $120.0983   $120.10   $120.10   $120.10  
  Purchase #6 $202.55   11.512%   $225.8676   $225.87   $225.85   $225.90  
  Purchase #7 $201.95   5.547%   $213.1522   $213.15   $213.15   $213.20  
  7 purchase totals = $954.49       $1,036.2017   $1,036.21   $1,036.15   $1,036.20