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	$113.35	9.237%	$123.8201	$123.82	$123.80	$123.80
Purchase #2	$198.58	6.250%	$210.9913	$210.99	$211.00	$211.00
Purchase #3	$167.95	13.160%	$190.0522	$190.05	$190.05	$190.10
Purchase #4	$83.88	8.870%	$91.3202	$91.32	$91.30	$91.30
Purchase #5	$173.52	12.152%	$194.6062	$194.61	$194.60	$194.60
Purchase #6	$80.64	13.180%	$91.2684	$91.27	$91.25	$91.30
Purchase #7	$47.61	12.273%	$53.4532	$53.45	$53.45	$53.50
7 purchase totals =	$865.53		$955.5116	$955.51	$955.45	$955.60