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 $180.32   8.325%   $195.3316   $195.33   $195.35   $195.30  
  Purchase #2 $214.70   9.122%   $234.2849   $234.28   $234.30   $234.30  
  Purchase #3 $244.32   13.183%   $276.5287   $276.53   $276.55   $276.50  
  Purchase #4 $136.78   11.438%   $152.4249   $152.42   $152.40   $152.40  
  Purchase #5 $150.26   7.149%   $161.0021   $161.00   $161.00   $161.00  
  Purchase #6 $29.25   10.171%   $32.225   $32.23   $32.25   $32.20  
  Purchase #7 $245.55   7.834%   $264.7864   $264.79   $264.80   $264.80  
  7 purchase totals = $1,201.18       $1,316.5836   $1,316.58   $1,316.65   $1,316.50