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 $213.68   8.836%   $232.5608   $232.56   $232.55   $232.60  
  Purchase #2 $195.73   5.398%   $206.2955   $206.30   $206.30   $206.30  
  Purchase #3 $62.52   11.713%   $69.843   $69.84   $69.85   $69.80  
  Purchase #4 $125.51   11.711%   $140.2085   $140.21   $140.20   $140.20  
  Purchase #5 $156.68   6.358%   $166.6417   $166.64   $166.65   $166.60  
  Purchase #6 $162.65   5.814%   $172.1065   $172.11   $172.10   $172.10  
  Purchase #7 $212.80   6.647%   $226.9448   $226.94   $226.95   $226.90  
  7 purchase totals = $1,129.57       $1,214.6008   $1,214.60   $1,214.60   $1,214.50