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	$243.33	4.408%	$254.056	$254.06	$254.05	$254.10
Purchase #2	$35.43	6.195%	$37.6249	$37.62	$37.60	$37.60
Purchase #3	$90.74	10.750%	$100.4946	$100.49	$100.50	$100.50
Purchase #4	$194.95	12.405%	$219.1335	$219.13	$219.15	$219.10
Purchase #5	$68.95	5.798%	$72.9477	$72.95	$72.95	$72.90
Purchase #6	$169.89	12.306%	$190.7967	$190.80	$190.80	$190.80
Purchase #7	$117.37	10.168%	$129.3042	$129.30	$129.30	$129.30
7 purchase totals =	$920.66		$1,004.3576	$1,004.35	$1,004.35	$1,004.30