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	$151.61	4.871%	$158.9949	$158.99	$159.00	$159.00
Purchase #2	$191.45	4.798%	$200.6358	$200.64	$200.65	$200.60
Purchase #3	$193.76	10.304%	$213.725	$213.73	$213.75	$213.70
Purchase #4	$216.69	7.846%	$233.6915	$233.69	$233.70	$233.70
Purchase #5	$66.38	9.468%	$72.6649	$72.66	$72.65	$72.70
Purchase #6	$235.82	3.244%	$243.47	$243.47	$243.45	$243.50
Purchase #7	$168.54	13.321%	$190.9912	$190.99	$191.00	$191.00
7 purchase totals =	$1,224.25		$1,314.1733	$1,314.17	$1,314.20	$1,314.20