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 $83.57   12.431%   $93.9586   $93.96   $93.95   $94.00  
  Purchase #2 $35.60   8.781%   $38.726   $38.73   $38.75   $38.70  
  Purchase #3 $150.77   3.591%   $156.1842   $156.18   $156.20   $156.20  
  Purchase #4 $186.93   5.802%   $197.7757   $197.78   $197.80   $197.80  
  Purchase #5 $174.68   12.299%   $196.1639   $196.16   $196.15   $196.20  
  Purchase #6 $234.30   3.148%   $241.6758   $241.68   $241.70   $241.70  
  Purchase #7 $169.52   4.709%   $177.5027   $177.50   $177.50   $177.50  
  7 purchase totals = $1,035.37       $1,101.9869   $1,101.99   $1,102.05   $1,102.10