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 $86.63   12.673%   $97.6086   $97.61   $97.60   $97.60  
  Purchase #2 $31.95   9.638%   $35.0293   $35.03   $35.05   $35.00  
  Purchase #3 $144.93   3.268%   $149.6663   $149.67   $149.65   $149.70  
  Purchase #4 $228.99   4.744%   $239.8533   $239.85   $239.85   $239.90  
  Purchase #5 $210.95   5.762%   $223.1049   $223.10   $223.10   $223.10  
  Purchase #6 $90.49   6.750%   $96.5981   $96.60   $96.60   $96.60  
  Purchase #7 $195.52   7.707%   $210.5887   $210.59   $210.60   $210.60  
  7 purchase totals = $989.46       $1,052.4492   $1,052.45   $1,052.45   $1,052.50