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 $61.95   8.230%   $67.0485   $67.05   $67.05   $67.00  
  Purchase #2 $23.30   3.831%   $24.1926   $24.19   $24.20   $24.20  
  Purchase #3 $186.85   13.484%   $212.0449   $212.04   $212.05   $212.00  
  Purchase #4 $226.55   8.327%   $245.4148   $245.41   $245.40   $245.40  
  Purchase #5 $21.49   13.609%   $24.4146   $24.41   $24.40   $24.40  
  Purchase #6 $241.31   8.845%   $262.6539   $262.65   $262.65   $262.70  
  Purchase #7 $249.74   6.319%   $265.5211   $265.52   $265.50   $265.50  
  7 purchase totals = $1,011.19       $1,101.2904   $1,101.27   $1,101.25   $1,101.20