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 $173.67   12.169%   $194.8039   $194.80   $194.80   $194.80  
  Purchase #2 $43.61   3.486%   $45.1302   $45.13   $45.15   $45.10  
  Purchase #3 $113.52   3.395%   $117.374   $117.37   $117.35   $117.40  
  Purchase #4 $6.87   4.772%   $7.1978   $7.20   $7.20   $7.20  
  Purchase #5 $129.46   10.618%   $143.2061   $143.21   $143.20   $143.20  
  Purchase #6 $241.45   3.155%   $249.0677   $249.07   $249.05   $249.10  
  Purchase #7 $244.57   5.170%   $257.2143   $257.21   $257.20   $257.20  
  7 purchase totals = $953.15       $1,013.9940   $1,013.99   $1,013.95   $1,014.00