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	$94.28	12.564%	$106.1253	$106.13	$106.15	$106.10
Purchase #2	$190.61	3.640%	$197.5482	$197.55	$197.55	$197.50
Purchase #3	$101.61	3.139%	$104.7995	$104.80	$104.80	$104.80
Purchase #4	$153.87	8.842%	$167.4752	$167.48	$167.50	$167.50
Purchase #5	$57.77	3.455%	$59.766	$59.77	$59.75	$59.80
Purchase #6	$165.97	5.872%	$175.7158	$175.72	$175.70	$175.70
Purchase #7	$133.28	13.507%	$151.2821	$151.28	$151.30	$151.30
7 purchase totals =	$897.39		$962.7121	$962.73	$962.75	$962.70