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 $162.74   8.650%   $176.817   $176.82   $176.80   $176.80  
  Purchase #2 $51.93   5.431%   $54.7503   $54.75   $54.75   $54.80  
  Purchase #3 $238.39   3.308%   $246.2759   $246.28   $246.30   $246.30  
  Purchase #4 $120.71   6.769%   $128.8809   $128.88   $128.90   $128.90  
  Purchase #5 $187.67   3.260%   $193.788   $193.79   $193.80   $193.80  
  Purchase #6 $212.78   6.721%   $227.0809   $227.08   $227.10   $227.10  
  Purchase #7 $108.91   12.809%   $122.8603   $122.86   $122.85   $122.90  
  7 purchase totals = $1,083.13       $1,150.4533   $1,150.46   $1,150.50   $1,150.60