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	$181.65	13.300%	$205.8095	$205.81	$205.80	$205.80
Purchase #2	$170.80	9.265%	$186.6246	$186.62	$186.60	$186.60
Purchase #3	$95.67	4.624%	$100.0938	$100.09	$100.10	$100.10
Purchase #4	$197.54	7.203%	$211.7688	$211.77	$211.75	$211.80
Purchase #5	$235.27	9.166%	$256.8348	$256.83	$256.85	$256.80
Purchase #6	$171.37	12.437%	$192.6833	$192.68	$192.70	$192.70
Purchase #7	$39.56	7.594%	$42.5642	$42.56	$42.55	$42.60
7 purchase totals =	$1,091.86		$1,196.3790	$1,196.36	$1,196.35	$1,196.40