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 $87.93   10.145%   $96.8505   $96.85   $96.85   $96.90  
  Purchase #2 $223.34   12.385%   $251.0007   $251.00   $251.00   $251.00  
  Purchase #3 $215.62   10.114%   $237.4278   $237.43   $237.45   $237.40  
  Purchase #4 $44.62   3.278%   $46.0826   $46.08   $46.10   $46.10  
  Purchase #5 $206.43   3.609%   $213.8801   $213.88   $213.90   $213.90  
  Purchase #6 $45.98   13.824%   $52.3363   $52.34   $52.35   $52.30  
  Purchase #7 $241.26   6.109%   $255.9986   $256.00   $256.00   $256.00  
  7 purchase totals = $1,065.18       $1,153.5766   $1,153.58   $1,153.65   $1,153.60