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	$145.92	10.275%	$160.9133	$160.91	$160.90	$160.90
Purchase #2	$229.71	11.155%	$255.3342	$255.33	$255.35	$255.30
Purchase #3	$59.50	3.333%	$61.4831	$61.48	$61.50	$61.50
Purchase #4	$33.65	4.700%	$35.2316	$35.23	$35.25	$35.20
Purchase #5	$161.25	11.517%	$179.8212	$179.82	$179.80	$179.80
Purchase #6	$219.99	5.324%	$231.7023	$231.70	$231.70	$231.70
Purchase #7	$53.31	9.543%	$58.3974	$58.40	$58.40	$58.40
7 purchase totals =	$903.33		$982.8831	$982.87	$982.90	$982.80