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	$219.76	5.104%	$230.9766	$230.98	$231.00	$231.00
Purchase #2	$178.63	11.332%	$198.8724	$198.87	$198.85	$198.90
Purchase #3	$67.93	13.816%	$77.3152	$77.32	$77.30	$77.30
Purchase #4	$41.61	3.130%	$42.9124	$42.91	$42.90	$42.90
Purchase #5	$169.82	13.839%	$193.3214	$193.32	$193.30	$193.30
Purchase #6	$146.55	3.557%	$151.7628	$151.76	$151.75	$151.80
Purchase #7	$235.92	6.439%	$251.1109	$251.11	$251.10	$251.10
7 purchase totals =	$1,060.22		$1,146.2717	$1,146.27	$1,146.20	$1,146.30