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	$106.89	9.797%	$117.362	$117.36	$117.35	$117.40
Purchase #2	$37.71	4.842%	$39.5359	$39.54	$39.55	$39.50
Purchase #3	$165.58	5.384%	$174.4948	$174.49	$174.50	$174.50
Purchase #4	$120.69	5.739%	$127.6164	$127.62	$127.60	$127.60
Purchase #5	$117.61	13.232%	$133.1722	$133.17	$133.15	$133.20
Purchase #6	$6.90	5.110%	$7.2526	$7.25	$7.25	$7.30
Purchase #7	$52.59	3.168%	$54.2561	$54.26	$54.25	$54.30
7 purchase totals =	$607.97		$653.6900	$653.69	$653.65	$653.80