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	$177.32	13.290%	$200.8858	$200.89	$200.90	$200.90
Purchase #2	$134.82	12.512%	$151.6887	$151.69	$151.70	$151.70
Purchase #3	$56.56	13.253%	$64.0559	$64.06	$64.05	$64.10
Purchase #4	$95.62	3.554%	$99.0183	$99.02	$99.00	$99.00
Purchase #5	$185.65	4.517%	$194.0358	$194.04	$194.05	$194.00
Purchase #6	$145.26	10.787%	$160.9292	$160.93	$160.95	$160.90
Purchase #7	$121.29	11.170%	$134.8381	$134.84	$134.85	$134.80
7 purchase totals =	$916.52		$1,005.4518	$1,005.47	$1,005.50	$1,005.40