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 $113.27   4.833%   $118.7443   $118.74   $118.75   $118.70  
  Purchase #2 $58.60   7.411%   $62.9428   $62.94   $62.95   $62.90  
  Purchase #3 $80.51   6.812%   $85.9943   $85.99   $86.00   $86.00  
  Purchase #4 $225.79   7.157%   $241.9498   $241.95   $241.95   $241.90  
  Purchase #5 $230.30   7.342%   $247.2086   $247.21   $247.20   $247.20  
  Purchase #6 $204.75   3.679%   $212.2828   $212.28   $212.30   $212.30  
  Purchase #7 $53.48   4.447%   $55.8583   $55.86   $55.85   $55.90  
  7 purchase totals = $966.70       $1,024.9809   $1,024.97   $1,025.00   $1,024.90