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	$120.54	11.590%	$134.5106	$134.51	$134.50	$134.50
Purchase #2	$58.57	11.205%	$65.1328	$65.13	$65.15	$65.10
Purchase #3	$167.60	3.557%	$173.5615	$173.56	$173.55	$173.60
Purchase #4	$211.97	5.504%	$223.6368	$223.64	$223.65	$223.60
Purchase #5	$244.35	8.152%	$264.2694	$264.27	$264.25	$264.30
Purchase #6	$162.67	10.116%	$179.1257	$179.13	$179.15	$179.10
Purchase #7	$139.92	5.264%	$147.2854	$147.29	$147.30	$147.30
7 purchase totals =	$1,105.62		$1,187.5222	$1,187.53	$1,187.55	$1,187.50