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	$151.56	5.421%	$159.7761	$159.78	$159.80	$159.80
Purchase #2	$111.26	4.426%	$116.1844	$116.18	$116.20	$116.20
Purchase #3	$18.87	10.408%	$20.834	$20.83	$20.85	$20.80
Purchase #4	$152.89	10.220%	$168.5154	$168.52	$168.50	$168.50
Purchase #5	$38.77	5.677%	$40.971	$40.97	$40.95	$41.00
Purchase #6	$69.31	3.518%	$71.7483	$71.75	$71.75	$71.70
Purchase #7	$219.65	6.801%	$234.5884	$234.59	$234.60	$234.60
7 purchase totals =	$762.31		$812.6176	$812.62	$812.65	$812.60