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	$151.77	12.598%	$170.89	$170.89	$170.90	$170.90
Purchase #2	$120.64	5.707%	$127.5249	$127.52	$127.50	$127.50
Purchase #3	$122.70	5.103%	$128.9614	$128.96	$128.95	$129.00
Purchase #4	$67.51	13.275%	$76.472	$76.47	$76.45	$76.50
Purchase #5	$54.71	4.650%	$57.254	$57.25	$57.25	$57.30
Purchase #6	$167.51	13.522%	$190.1607	$190.16	$190.15	$190.20
Purchase #7	$178.62	10.270%	$196.9643	$196.96	$196.95	$197.00
7 purchase totals =	$863.46		$948.2273	$948.21	$948.15	$948.40