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 $61.50   11.810%   $68.7632   $68.76   $68.75   $68.80  
  Purchase #2 $227.43   12.156%   $255.0764   $255.08   $255.10   $255.10  
  Purchase #3 $220.29   5.492%   $232.3883   $232.39   $232.40   $232.40  
  Purchase #4 $68.52   3.424%   $70.8661   $70.87   $70.85   $70.90  
  Purchase #5 $92.96   3.722%   $96.42   $96.42   $96.40   $96.40  
  Purchase #6 $185.63   8.379%   $201.1839   $201.18   $201.20   $201.20  
  Purchase #7 $173.64   6.140%   $184.3015   $184.30   $184.30   $184.30  
  7 purchase totals = $1,029.97       $1,108.9994   $1,109.00   $1,109.00   $1,109.10