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 $192.93   5.468%   $203.4794   $203.48   $203.50   $203.50  
  Purchase #2 $200.54   10.496%   $221.5887   $221.59   $221.60   $221.60  
  Purchase #3 $232.50   11.295%   $258.7609   $258.76   $258.75   $258.80  
  Purchase #4 $57.71   5.539%   $60.9066   $60.91   $60.90   $60.90  
  Purchase #5 $135.82   13.331%   $153.9262   $153.93   $153.95   $153.90  
  Purchase #6 $24.79   4.283%   $25.8518   $25.85   $25.85   $25.90  
  Purchase #7 $248.35   3.627%   $257.3577   $257.36   $257.35   $257.40  
  7 purchase totals = $1,092.64       $1,181.8713   $1,181.88   $1,181.90   $1,182.00