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	$208.72	11.429%	$232.5746	$232.57	$232.55	$232.60
Purchase #2	$23.83	7.485%	$25.6137	$25.61	$25.60	$25.60
Purchase #3	$104.80	7.437%	$112.594	$112.59	$112.60	$112.60
Purchase #4	$35.89	13.740%	$40.8213	$40.82	$40.80	$40.80
Purchase #5	$182.73	12.843%	$206.198	$206.20	$206.20	$206.20
Purchase #6	$155.59	5.868%	$164.72	$164.72	$164.70	$164.70
Purchase #7	$42.66	6.331%	$45.3608	$45.36	$45.35	$45.40
7 purchase totals =	$754.22		$827.8824	$827.87	$827.80	$827.90