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 $182.54   7.319%   $195.9001   $195.90   $195.90   $195.90  
  Purchase #2 $15.85   9.303%   $17.3245   $17.32   $17.30   $17.30  
  Purchase #3 $100.51   6.137%   $106.6783   $106.68   $106.70   $106.70  
  Purchase #4 $153.28   11.780%   $171.3364   $171.34   $171.35   $171.30  
  Purchase #5 $191.36   7.820%   $206.3244   $206.32   $206.30   $206.30  
  Purchase #6 $133.30   9.589%   $146.0821   $146.08   $146.10   $146.10  
  Purchase #7 $205.96   7.242%   $220.8756   $220.88   $220.90   $220.90  
  7 purchase totals = $982.80       $1,064.5214   $1,064.52   $1,064.55   $1,064.50