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	$198.34	10.325%	$218.8186	$218.82	$218.80	$218.80
Purchase #2	$57.80	4.863%	$60.6108	$60.61	$60.60	$60.60
Purchase #3	$184.95	8.378%	$200.4451	$200.45	$200.45	$200.40
Purchase #4	$171.26	12.297%	$192.3198	$192.32	$192.30	$192.30
Purchase #5	$160.49	4.103%	$167.0749	$167.07	$167.05	$167.10
Purchase #6	$124.91	9.512%	$136.7914	$136.79	$136.80	$136.80
Purchase #7	$83.25	11.156%	$92.5374	$92.54	$92.55	$92.50
7 purchase totals =	$981.00		$1,068.5980	$1,068.60	$1,068.55	$1,068.50