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	$191.63	9.366%	$209.5781	$209.58	$209.60	$209.60
Purchase #2	$60.74	6.637%	$64.7713	$64.77	$64.75	$64.80
Purchase #3	$107.91	9.231%	$117.8712	$117.87	$117.85	$117.90
Purchase #4	$230.78	12.174%	$258.8752	$258.88	$258.90	$258.90
Purchase #5	$33.39	10.391%	$36.8596	$36.86	$36.85	$36.90
Purchase #6	$157.52	4.479%	$164.5753	$164.58	$164.60	$164.60
Purchase #7	$196.38	13.573%	$223.0347	$223.03	$223.05	$223.00
7 purchase totals =	$978.35		$1,075.5654	$1,075.57	$1,075.60	$1,075.70