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 $95.59   5.321%   $100.6763   $100.68   $100.70   $100.70  
  Purchase #2 $242.42   11.146%   $269.4401   $269.44   $269.45   $269.40  
  Purchase #3 $77.83   3.666%   $80.6832   $80.68   $80.70   $80.70  
  Purchase #4 $245.97   6.572%   $262.1351   $262.14   $262.15   $262.10  
  Purchase #5 $148.35   6.434%   $157.8948   $157.89   $157.90   $157.90  
  Purchase #6 $45.94   5.606%   $48.5154   $48.52   $48.50   $48.50  
  Purchase #7 $184.30   5.452%   $194.348   $194.35   $194.35   $194.30  
  7 purchase totals = $1,040.40       $1,113.6929   $1,113.70   $1,113.75   $1,113.60