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	$103.48	7.639%	$111.3848	$111.38	$111.40	$111.40
Purchase #2	$53.33	10.770%	$59.0736	$59.07	$59.05	$59.10
Purchase #3	$146.65	7.182%	$157.1824	$157.18	$157.20	$157.20
Purchase #4	$203.88	7.538%	$219.2485	$219.25	$219.25	$219.20
Purchase #5	$141.61	13.344%	$160.5064	$160.51	$160.50	$160.50
Purchase #6	$227.68	4.589%	$238.1282	$238.13	$238.15	$238.10
Purchase #7	$149.93	7.313%	$160.8944	$160.89	$160.90	$160.90
7 purchase totals =	$1,026.56		$1,106.4183	$1,106.41	$1,106.45	$1,106.40