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 $53.32   4.763%   $55.8596   $55.86   $55.85   $55.90  
  Purchase #2 $72.43   9.190%   $79.0863   $79.09   $79.10   $79.10  
  Purchase #3 $213.66   5.289%   $224.9605   $224.96   $224.95   $225.00  
  Purchase #4 $209.91   5.108%   $220.6322   $220.63   $220.65   $220.60  
  Purchase #5 $50.64   11.843%   $56.6373   $56.64   $56.65   $56.60  
  Purchase #6 $244.84   7.313%   $262.7451   $262.75   $262.75   $262.70  
  Purchase #7 $153.73   8.870%   $167.3659   $167.37   $167.35   $167.40  
  7 purchase totals = $998.53       $1,067.2869   $1,067.30   $1,067.30   $1,067.30