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	$220.26	7.670%	$237.1539	$237.15	$237.15	$237.20
Purchase #2	$177.88	12.144%	$199.4817	$199.48	$199.50	$199.50
Purchase #3	$210.43	6.187%	$223.4493	$223.45	$223.45	$223.40
Purchase #4	$144.31	5.757%	$152.6179	$152.62	$152.60	$152.60
Purchase #5	$160.55	7.506%	$172.6009	$172.60	$172.60	$172.60
Purchase #6	$47.85	12.469%	$53.8164	$53.82	$53.80	$53.80
Purchase #7	$77.90	9.742%	$85.489	$85.49	$85.50	$85.50
7 purchase totals =	$1,039.18		$1,124.6091	$1,124.61	$1,124.60	$1,124.60