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 $197.53   12.755%   $222.725   $222.73   $222.75   $222.70  
  Purchase #2 $48.31   11.697%   $53.9608   $53.96   $53.95   $54.00  
  Purchase #3 $223.53   3.740%   $231.89   $231.89   $231.90   $231.90  
  Purchase #4 $169.94   7.858%   $183.2939   $183.29   $183.30   $183.30  
  Purchase #5 $76.41   7.350%   $82.0261   $82.03   $82.05   $82.00  
  Purchase #6 $115.79   12.321%   $130.0565   $130.06   $130.05   $130.10  
  Purchase #7 $205.37   6.190%   $218.0824   $218.08   $218.10   $218.10  
  7 purchase totals = $1,036.88       $1,122.0347   $1,122.04   $1,122.10   $1,122.10