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	$142.75	10.394%	$157.5874	$157.59	$157.60	$157.60
Purchase #2	$181.91	4.768%	$190.5835	$190.58	$190.60	$190.60
Purchase #3	$229.47	5.627%	$242.3823	$242.38	$242.40	$242.40
Purchase #4	$147.82	13.385%	$167.6057	$167.61	$167.60	$167.60
Purchase #5	$162.81	5.675%	$172.0495	$172.05	$172.05	$172.00
Purchase #6	$248.95	10.773%	$275.7694	$275.77	$275.75	$275.80
Purchase #7	$122.62	4.564%	$128.2164	$128.22	$128.20	$128.20
7 purchase totals =	$1,236.33		$1,334.1942	$1,334.20	$1,334.20	$1,334.20