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	$143.82	8.479%	$156.0145	$156.01	$156.00	$156.00
Purchase #2	$175.69	5.639%	$185.5972	$185.60	$185.60	$185.60
Purchase #3	$208.81	12.422%	$234.7484	$234.75	$234.75	$234.70
Purchase #4	$214.54	5.138%	$225.5631	$225.56	$225.55	$225.60
Purchase #5	$204.37	7.801%	$220.3129	$220.31	$220.30	$220.30
Purchase #6	$9.72	13.376%	$11.0201	$11.02	$11.00	$11.00
Purchase #7	$62.45	7.425%	$67.0869	$67.09	$67.10	$67.10
7 purchase totals =	$1,019.40		$1,100.3431	$1,100.34	$1,100.30	$1,100.30