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 $66.91   11.141%   $74.3644   $74.36   $74.35   $74.40  
  Purchase #2 $210.69   3.279%   $217.5985   $217.60   $217.60   $217.60  
  Purchase #3 $55.59   8.253%   $60.1778   $60.18   $60.20   $60.20  
  Purchase #4 $73.52   4.829%   $77.0703   $77.07   $77.05   $77.10  
  Purchase #5 $211.86   10.409%   $233.9125   $233.91   $233.90   $233.90  
  Purchase #6 $165.64   10.821%   $183.5639   $183.56   $183.55   $183.60  
  Purchase #7 $192.88   6.132%   $204.7074   $204.71   $204.70   $204.70  
  7 purchase totals = $977.09       $1,051.3948   $1,051.39   $1,051.35   $1,051.50