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 $228.99   7.670%   $246.5535   $246.55   $246.55   $246.60  
  Purchase #2 $63.30   3.204%   $65.3281   $65.33   $65.35   $65.30  
  Purchase #3 $159.74   4.637%   $167.1471   $167.15   $167.15   $167.10  
  Purchase #4 $183.52   3.790%   $190.4754   $190.48   $190.50   $190.50  
  Purchase #5 $41.96   9.817%   $46.0792   $46.08   $46.10   $46.10  
  Purchase #6 $26.87   6.296%   $28.5617   $28.56   $28.55   $28.60  
  Purchase #7 $247.36   9.151%   $269.9959   $270.00   $270.00   $270.00  
  7 purchase totals = $951.74       $1,014.1409   $1,014.15   $1,014.20   $1,014.20