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 $214.53   8.745%   $233.2906   $233.29   $233.30   $233.30  
  Purchase #2 $179.58   5.609%   $189.6526   $189.65   $189.65   $189.70  
  Purchase #3 $81.47   8.265%   $88.2035   $88.20   $88.20   $88.20  
  Purchase #4 $138.35   12.184%   $155.2066   $155.21   $155.20   $155.20  
  Purchase #5 $203.81   9.584%   $223.3432   $223.34   $223.35   $223.30  
  Purchase #6 $9.32   9.662%   $10.2205   $10.22   $10.20   $10.20  
  Purchase #7 $189.98   8.600%   $206.3183   $206.32   $206.30   $206.30  
  7 purchase totals = $1,017.04       $1,106.2353   $1,106.23   $1,106.20   $1,106.20