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	$222.38	12.352%	$249.8484	$249.85	$249.85	$249.80
Purchase #2	$151.96	3.711%	$157.5992	$157.60	$157.60	$157.60
Purchase #3	$50.27	7.722%	$54.1518	$54.15	$54.15	$54.20
Purchase #4	$107.51	12.761%	$121.2294	$121.23	$121.25	$121.20
Purchase #5	$141.30	7.852%	$152.3949	$152.39	$152.40	$152.40
Purchase #6	$181.95	10.415%	$200.9001	$200.90	$200.90	$200.90
Purchase #7	$101.97	9.234%	$111.3859	$111.39	$111.40	$111.40
7 purchase totals =	$957.34		$1,047.5097	$1,047.51	$1,047.55	$1,047.50