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	$145.95	4.489%	$152.5017	$152.50	$152.50	$152.50
Purchase #2	$162.77	10.580%	$179.9911	$179.99	$180.00	$180.00
Purchase #3	$74.51	5.358%	$78.5022	$78.50	$78.50	$78.50
Purchase #4	$32.31	4.627%	$33.805	$33.81	$33.80	$33.80
Purchase #5	$132.43	13.267%	$149.9995	$150.00	$150.00	$150.00
Purchase #6	$192.78	10.753%	$213.5096	$213.51	$213.50	$213.50
Purchase #7	$219.55	3.583%	$227.4165	$227.42	$227.40	$227.40
7 purchase totals =	$960.30		$1,035.7256	$1,035.73	$1,035.70	$1,035.70