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 $48.52   8.325%   $52.5593   $52.56   $52.55   $52.60  
  Purchase #2 $132.31   10.272%   $145.9009   $145.90   $145.90   $145.90  
  Purchase #3 $58.48   11.847%   $65.4081   $65.41   $65.40   $65.40  
  Purchase #4 $136.47   4.121%   $142.0939   $142.09   $142.10   $142.10  
  Purchase #5 $188.43   7.288%   $202.1628   $202.16   $202.15   $202.20  
  Purchase #6 $230.37   13.130%   $260.6176   $260.62   $260.60   $260.60  
  Purchase #7 $179.88   9.815%   $197.5352   $197.54   $197.55   $197.50  
  7 purchase totals = $974.46       $1,066.2778   $1,066.28   $1,066.25   $1,066.30