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 $74.52   11.188%   $82.8573   $82.86   $82.85   $82.90  
  Purchase #2 $16.76   4.752%   $17.5564   $17.56   $17.55   $17.60  
  Purchase #3 $93.85   4.772%   $98.3285   $98.33   $98.35   $98.30  
  Purchase #4 $214.79   3.829%   $223.0143   $223.01   $223.00   $223.00  
  Purchase #5 $150.90   10.701%   $167.0478   $167.05   $167.05   $167.00  
  Purchase #6 $209.85   3.162%   $216.4855   $216.49   $216.50   $216.50  
  Purchase #7 $180.50   11.719%   $201.6528   $201.65   $201.65   $201.70  
  7 purchase totals = $941.17       $1,006.9426   $1,006.95   $1,006.95   $1,007.00