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	$34.25	4.133%	$35.6656	$35.67	$35.65	$35.70
Purchase #2	$210.70	5.626%	$222.554	$222.55	$222.55	$222.60
Purchase #3	$195.67	5.733%	$206.8878	$206.89	$206.90	$206.90
Purchase #4	$146.45	13.635%	$166.4185	$166.42	$166.40	$166.40
Purchase #5	$91.57	11.772%	$102.3496	$102.35	$102.35	$102.30
Purchase #6	$141.81	3.134%	$146.2543	$146.25	$146.25	$146.30
Purchase #7	$133.33	11.483%	$148.6403	$148.64	$148.65	$148.60
7 purchase totals =	$953.78		$1,028.7701	$1,028.77	$1,028.75	$1,028.80