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	$216.54	10.267%	$238.7722	$238.77	$238.75	$238.80
Purchase #2	$116.51	10.184%	$128.3754	$128.38	$128.40	$128.40
Purchase #3	$94.92	4.871%	$99.5436	$99.54	$99.55	$99.50
Purchase #4	$216.35	4.114%	$225.2506	$225.25	$225.25	$225.30
Purchase #5	$151.96	10.530%	$167.9614	$167.96	$167.95	$168.00
Purchase #6	$152.73	3.378%	$157.8892	$157.89	$157.90	$157.90
Purchase #7	$18.65	5.163%	$19.6129	$19.61	$19.60	$19.60
7 purchase totals =	$967.66		$1,037.4053	$1,037.40	$1,037.40	$1,037.50