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	$177.71	11.785%	$198.6531	$198.65	$198.65	$198.70
Purchase #2	$164.83	8.806%	$179.3449	$179.34	$179.35	$179.30
Purchase #3	$48.93	13.450%	$55.5111	$55.51	$55.50	$55.50
Purchase #4	$247.91	4.428%	$258.8875	$258.89	$258.90	$258.90
Purchase #5	$61.92	8.408%	$67.1262	$67.13	$67.15	$67.10
Purchase #6	$54.94	9.773%	$60.3093	$60.31	$60.30	$60.30
Purchase #7	$76.85	8.583%	$83.446	$83.45	$83.45	$83.40
7 purchase totals =	$833.09		$903.2781	$903.28	$903.30	$903.20