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 $47.47   3.282%   $49.028   $49.03   $49.05   $49.00  
  Purchase #2 $231.44   3.485%   $239.5057   $239.51   $239.50   $239.50  
  Purchase #3 $38.72   4.680%   $40.5321   $40.53   $40.55   $40.50  
  Purchase #4 $159.52   13.569%   $181.1653   $181.17   $181.15   $181.20  
  Purchase #5 $156.87   9.145%   $171.2158   $171.22   $171.20   $171.20  
  Purchase #6 $245.47   11.394%   $273.4389   $273.44   $273.45   $273.40  
  Purchase #7 $178.59   13.220%   $202.1996   $202.20   $202.20   $202.20  
  7 purchase totals = $1,058.08       $1,157.0854   $1,157.10   $1,157.10   $1,157.00