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 $43.44   8.523%   $47.1424   $47.14   $47.15   $47.10  
  Purchase #2 $237.98   5.640%   $251.4021   $251.40   $251.40   $251.40  
  Purchase #3 $67.67   5.776%   $71.5786   $71.58   $71.60   $71.60  
  Purchase #4 $225.86   9.254%   $246.7611   $246.76   $246.75   $246.80  
  Purchase #5 $232.41   12.824%   $262.2143   $262.21   $262.20   $262.20  
  Purchase #6 $132.48   9.713%   $145.3478   $145.35   $145.35   $145.30  
  Purchase #7 $230.91   7.227%   $247.5979   $247.60   $247.60   $247.60  
  7 purchase totals = $1,170.75       $1,272.0442   $1,272.04   $1,272.05   $1,272.00