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 $181.33   6.399%   $192.9333   $192.93   $192.95   $192.90  
  Purchase #2 $234.96   4.401%   $245.3006   $245.30   $245.30   $245.30  
  Purchase #3 $10.52   9.404%   $11.5093   $11.51   $11.50   $11.50  
  Purchase #4 $146.69   3.230%   $151.4281   $151.43   $151.45   $151.40  
  Purchase #5 $163.66   5.325%   $172.3749   $172.37   $172.35   $172.40  
  Purchase #6 $90.53   11.672%   $101.0967   $101.10   $101.10   $101.10  
  Purchase #7 $73.59   8.145%   $79.5839   $79.58   $79.60   $79.60  
  7 purchase totals = $901.28       $954.2268   $954.22   $954.25   $954.20