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	$43.54	10.772%	$48.2301	$48.23	$48.25	$48.20
Purchase #2	$42.66	7.557%	$45.8838	$45.88	$45.90	$45.90
Purchase #3	$82.31	8.537%	$89.3368	$89.34	$89.35	$89.30
Purchase #4	$236.59	11.491%	$263.7766	$263.78	$263.80	$263.80
Purchase #5	$92.37	8.554%	$100.2713	$100.27	$100.25	$100.30
Purchase #6	$95.29	12.153%	$106.8706	$106.87	$106.85	$106.90
Purchase #7	$230.55	7.205%	$247.1611	$247.16	$247.15	$247.20
7 purchase totals =	$823.31		$901.5303	$901.53	$901.55	$901.60