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	$179.60	3.236%	$185.4119	$185.41	$185.40	$185.40
Purchase #2	$147.83	4.113%	$153.9102	$153.91	$153.90	$153.90
Purchase #3	$110.84	5.102%	$116.4951	$116.50	$116.50	$116.50
Purchase #4	$148.58	11.341%	$165.4305	$165.43	$165.45	$165.40
Purchase #5	$250.65	12.444%	$281.8409	$281.84	$281.85	$281.80
Purchase #6	$153.92	7.155%	$164.933	$164.93	$164.95	$164.90
Purchase #7	$136.36	7.530%	$146.6279	$146.63	$146.65	$146.60
7 purchase totals =	$1,127.78		$1,214.6495	$1,214.65	$1,214.70	$1,214.50