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 $84.79   12.392%   $95.2972   $95.30   $95.30   $95.30  
  Purchase #2 $91.56   11.727%   $102.2972   $102.30   $102.30   $102.30  
  Purchase #3 $242.35   13.625%   $275.3702   $275.37   $275.35   $275.40  
  Purchase #4 $25.77   6.503%   $27.4458   $27.45   $27.45   $27.40  
  Purchase #5 $198.89   5.376%   $209.5823   $209.58   $209.60   $209.60  
  Purchase #6 $229.77   7.731%   $247.5335   $247.53   $247.55   $247.50  
  Purchase #7 $77.27   12.597%   $87.0037   $87.00   $87.00   $87.00  
  7 purchase totals = $950.40       $1,044.5299   $1,044.53   $1,044.55   $1,044.50