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 $87.90   7.619%   $94.5971   $94.60   $94.60   $94.60  
  Purchase #2 $97.74   4.193%   $101.8382   $101.84   $101.85   $101.80  
  Purchase #3 $217.76   5.753%   $230.2877   $230.29   $230.30   $230.30  
  Purchase #4 $48.29   5.328%   $50.8629   $50.86   $50.85   $50.90  
  Purchase #5 $91.51   5.495%   $96.5385   $96.54   $96.55   $96.50  
  Purchase #6 $234.86   12.679%   $264.6379   $264.64   $264.65   $264.60  
  Purchase #7 $202.50   5.195%   $213.0199   $213.02   $213.00   $213.00  
  7 purchase totals = $980.56       $1,051.7822   $1,051.79   $1,051.80   $1,051.70