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	$79.95	9.380%	$87.4493	$87.45	$87.45	$87.40
Purchase #2	$64.34	4.522%	$67.2495	$67.25	$67.25	$67.20
Purchase #3	$214.61	6.429%	$228.4073	$228.41	$228.40	$228.40
Purchase #4	$165.27	4.461%	$172.6427	$172.64	$172.65	$172.60
Purchase #5	$233.48	12.150%	$261.8478	$261.85	$261.85	$261.80
Purchase #6	$50.33	7.440%	$54.0746	$54.07	$54.05	$54.10
Purchase #7	$6.37	11.780%	$7.1204	$7.12	$7.10	$7.10
7 purchase totals =	$814.35		$878.7916	$878.79	$878.75	$878.60