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	$175.36	12.257%	$196.8539	$196.85	$196.85	$196.90
Purchase #2	$113.82	11.710%	$127.1483	$127.15	$127.15	$127.10
Purchase #3	$132.76	9.431%	$145.2806	$145.28	$145.30	$145.30
Purchase #4	$243.36	11.140%	$270.4703	$270.47	$270.45	$270.50
Purchase #5	$208.95	13.865%	$237.9209	$237.92	$237.90	$237.90
Purchase #6	$34.42	8.747%	$37.4307	$37.43	$37.45	$37.40
Purchase #7	$131.47	4.250%	$137.0575	$137.06	$137.05	$137.10
7 purchase totals =	$1,040.14		$1,152.1622	$1,152.16	$1,152.15	$1,152.20