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	$120.60	5.564%	$127.3102	$127.31	$127.30	$127.30
Purchase #2	$78.33	3.340%	$80.9462	$80.95	$80.95	$80.90
Purchase #3	$76.73	11.662%	$85.6783	$85.68	$85.70	$85.70
Purchase #4	$55.77	8.760%	$60.6555	$60.66	$60.65	$60.70
Purchase #5	$110.30	6.138%	$117.0702	$117.07	$117.05	$117.10
Purchase #6	$35.78	5.653%	$37.8026	$37.80	$37.80	$37.80
Purchase #7	$222.29	7.295%	$238.5061	$238.51	$238.50	$238.50
7 purchase totals =	$699.80		$747.9691	$747.98	$747.95	$748.00