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	$132.65	7.388%	$142.4502	$142.45	$142.45	$142.50
Purchase #2	$145.74	3.284%	$150.5261	$150.53	$150.55	$150.50
Purchase #3	$155.68	4.485%	$162.6622	$162.66	$162.65	$162.70
Purchase #4	$102.93	7.573%	$110.7249	$110.72	$110.70	$110.70
Purchase #5	$115.35	10.622%	$127.6025	$127.60	$127.60	$127.60
Purchase #6	$33.30	7.729%	$35.8738	$35.87	$35.85	$35.90
Purchase #7	$93.44	5.435%	$98.5185	$98.52	$98.50	$98.50
7 purchase totals =	$779.09		$828.3582	$828.35	$828.30	$828.40