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	$195.68	12.404%	$219.9521	$219.95	$219.95	$220.00
Purchase #2	$57.61	3.493%	$59.6223	$59.62	$59.60	$59.60
Purchase #3	$111.90	12.678%	$126.0867	$126.09	$126.10	$126.10
Purchase #4	$140.56	11.788%	$157.1292	$157.13	$157.15	$157.10
Purchase #5	$180.46	6.246%	$191.7315	$191.73	$191.75	$191.70
Purchase #6	$212.69	10.469%	$234.9565	$234.96	$234.95	$235.00
Purchase #7	$83.98	7.784%	$90.517	$90.52	$90.50	$90.50
7 purchase totals =	$982.88		$1,079.9953	$1,080.00	$1,080.00	$1,080.00