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	$165.56	8.507%	$179.6442	$179.64	$179.65	$179.60
Purchase #2	$165.55	4.567%	$173.1107	$173.11	$173.10	$173.10
Purchase #3	$207.27	7.300%	$222.4007	$222.40	$222.40	$222.40
Purchase #4	$127.99	13.508%	$145.2789	$145.28	$145.30	$145.30
Purchase #5	$10.64	3.223%	$10.9829	$10.98	$11.00	$11.00
Purchase #6	$87.86	13.752%	$99.9425	$99.94	$99.95	$99.90
Purchase #7	$40.85	5.662%	$43.1629	$43.16	$43.15	$43.20
7 purchase totals =	$805.72		$874.5228	$874.51	$874.55	$874.50