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	$33.78	4.692%	$35.365	$35.37	$35.35	$35.40
Purchase #2	$96.47	3.140%	$99.4992	$99.50	$99.50	$99.50
Purchase #3	$116.91	10.229%	$128.8687	$128.87	$128.85	$128.90
Purchase #4	$172.97	12.178%	$194.0343	$194.03	$194.05	$194.00
Purchase #5	$148.76	6.664%	$158.6734	$158.67	$158.65	$158.70
Purchase #6	$179.87	3.150%	$185.5359	$185.54	$185.55	$185.50
Purchase #7	$105.37	6.439%	$112.1548	$112.15	$112.15	$112.20
7 purchase totals =	$854.13		$914.1313	$914.13	$914.10	$914.20