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 $192.41   11.735%   $214.9893   $214.99   $215.00   $215.00  
  Purchase #2 $118.90   7.351%   $127.6403   $127.64   $127.65   $127.60  
  Purchase #3 $174.36   4.700%   $182.5549   $182.55   $182.55   $182.60  
  Purchase #4 $88.72   5.313%   $93.4337   $93.43   $93.45   $93.40  
  Purchase #5 $137.78   11.160%   $153.1562   $153.16   $153.15   $153.20  
  Purchase #6 $181.95   11.439%   $202.7633   $202.76   $202.75   $202.80  
  Purchase #7 $138.41   13.809%   $157.523   $157.52   $157.50   $157.50  
  7 purchase totals = $1,032.53       $1,132.0607   $1,132.05   $1,132.05   $1,132.10