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 $60.74   5.627%   $64.1578   $64.16   $64.15   $64.20  
  Purchase #2 $211.67   10.133%   $233.1185   $233.12   $233.10   $233.10  
  Purchase #3 $62.36   9.194%   $68.0934   $68.09   $68.10   $68.10  
  Purchase #4 $84.48   11.764%   $94.4182   $94.42   $94.40   $94.40  
  Purchase #5 $226.68   10.690%   $250.9121   $250.91   $250.90   $250.90  
  Purchase #6 $66.54   13.525%   $75.5395   $75.54   $75.55   $75.50  
  Purchase #7 $213.57   6.869%   $228.2401   $228.24   $228.25   $228.20  
  7 purchase totals = $926.04       $1,014.4796   $1,014.48   $1,014.45   $1,014.40