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 $219.86   9.585%   $240.9336   $240.93   $240.95   $240.90  
  Purchase #2 $207.75   13.164%   $235.0982   $235.10   $235.10   $235.10  
  Purchase #3 $37.36   5.458%   $39.3991   $39.40   $39.40   $39.40  
  Purchase #4 $66.95   10.344%   $73.8753   $73.88   $73.90   $73.90  
  Purchase #5 $60.98   7.573%   $65.598   $65.60   $65.60   $65.60  
  Purchase #6 $203.70   4.828%   $213.5346   $213.53   $213.55   $213.50  
  Purchase #7 $149.67   11.571%   $166.9883   $166.99   $167.00   $167.00  
  7 purchase totals = $946.27       $1,035.4271   $1,035.43   $1,035.50   $1,035.40