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 $197.95   3.573%   $205.0228   $205.02   $205.00   $205.00  
  Purchase #2 $231.37   6.133%   $245.5599   $245.56   $245.55   $245.60  
  Purchase #3 $49.85   6.265%   $52.9731   $52.97   $52.95   $53.00  
  Purchase #4 $238.67   8.452%   $258.8424   $258.84   $258.85   $258.80  
  Purchase #5 $201.57   5.831%   $213.3235   $213.32   $213.30   $213.30  
  Purchase #6 $115.35   3.544%   $119.438   $119.44   $119.45   $119.40  
  Purchase #7 $20.57   6.651%   $21.9381   $21.94   $21.95   $21.90  
  7 purchase totals = $1,055.33       $1,117.0978   $1,117.09   $1,117.05   $1,117.00