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 $88.83   7.841%   $95.7952   $95.80   $95.80   $95.80  
  Purchase #2 $211.50   7.677%   $227.7369   $227.74   $227.75   $227.70  
  Purchase #3 $16.60   10.572%   $18.355   $18.36   $18.35   $18.40  
  Purchase #4 $203.33   8.188%   $219.9787   $219.98   $220.00   $220.00  
  Purchase #5 $158.54   10.222%   $174.746   $174.75   $174.75   $174.70  
  Purchase #6 $113.45   3.313%   $117.2086   $117.21   $117.20   $117.20  
  Purchase #7 $233.31   13.466%   $264.7275   $264.73   $264.75   $264.70  
  7 purchase totals = $1,025.56       $1,118.5479   $1,118.57   $1,118.60   $1,118.50