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 $63.61   9.796%   $69.8412   $69.84   $69.85   $69.80  
  Purchase #2 $140.64   9.348%   $153.787   $153.79   $153.80   $153.80  
  Purchase #3 $149.91   4.252%   $156.2842   $156.28   $156.30   $156.30  
  Purchase #4 $195.80   3.587%   $202.8233   $202.82   $202.80   $202.80  
  Purchase #5 $189.35   8.254%   $204.9789   $204.98   $205.00   $205.00  
  Purchase #6 $142.30   6.554%   $151.6263   $151.63   $151.65   $151.60  
  Purchase #7 $106.27   12.619%   $119.6802   $119.68   $119.70   $119.70  
  7 purchase totals = $987.88       $1,059.0211   $1,059.02   $1,059.10   $1,059.00