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	$204.98	4.415%	$214.0299	$214.03	$214.05	$214.00
Purchase #2	$35.64	5.297%	$37.5279	$37.53	$37.55	$37.50
Purchase #3	$126.78	12.295%	$142.3676	$142.37	$142.35	$142.40
Purchase #4	$191.86	8.585%	$208.3312	$208.33	$208.35	$208.30
Purchase #5	$137.82	11.503%	$153.6734	$153.67	$153.65	$153.70
Purchase #6	$29.73	8.198%	$32.1673	$32.17	$32.15	$32.20
Purchase #7	$164.57	4.110%	$171.3338	$171.33	$171.35	$171.30
7 purchase totals =	$891.38		$959.4311	$959.43	$959.45	$959.40