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	$180.32	11.199%	$200.514	$200.51	$200.50	$200.50
Purchase #2	$45.58	5.545%	$48.1074	$48.11	$48.10	$48.10
Purchase #3	$228.88	11.242%	$254.6107	$254.61	$254.60	$254.60
Purchase #4	$23.31	9.853%	$25.6067	$25.61	$25.60	$25.60
Purchase #5	$21.32	10.111%	$23.4757	$23.48	$23.50	$23.50
Purchase #6	$58.40	10.371%	$64.4567	$64.46	$64.45	$64.50
Purchase #7	$85.80	11.872%	$95.9862	$95.99	$96.00	$96.00
7 purchase totals =	$643.61		$712.7574	$712.77	$712.75	$712.80