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 $152.43   8.858%   $165.9322   $165.93   $165.95   $165.90  
  Purchase #2 $197.61   3.563%   $204.6508   $204.65   $204.65   $204.70  
  Purchase #3 $85.61   9.773%   $93.9767   $93.98   $94.00   $94.00  
  Purchase #4 $169.71   10.546%   $187.6076   $187.61   $187.60   $187.60  
  Purchase #5 $141.74   3.374%   $146.5223   $146.52   $146.50   $146.50  
  Purchase #6 $205.90   12.444%   $231.5222   $231.52   $231.50   $231.50  
  Purchase #7 $33.98   8.684%   $36.9308   $36.93   $36.95   $36.90  
  7 purchase totals = $986.98       $1,067.1426   $1,067.14   $1,067.15   $1,067.10