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 $72.36   3.120%   $74.6176   $74.62   $74.60   $74.60  
  Purchase #2 $156.25   3.347%   $161.4797   $161.48   $161.50   $161.50  
  Purchase #3 $195.39   3.686%   $202.5921   $202.59   $202.60   $202.60  
  Purchase #4 $23.79   4.411%   $24.8394   $24.84   $24.85   $24.80  
  Purchase #5 $239.25   6.325%   $254.3826   $254.38   $254.40   $254.40  
  Purchase #6 $173.82   11.442%   $193.7085   $193.71   $193.70   $193.70  
  Purchase #7 $167.52   13.735%   $190.5289   $190.53   $190.55   $190.50  
  7 purchase totals = $1,028.38       $1,102.1488   $1,102.15   $1,102.20   $1,102.10