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	$159.76	10.740%	$176.9182	$176.92	$176.90	$176.90
Purchase #2	$246.45	10.298%	$271.8294	$271.83	$271.85	$271.80
Purchase #3	$249.31	13.422%	$282.7724	$282.77	$282.75	$282.80
Purchase #4	$171.80	4.329%	$179.2372	$179.24	$179.25	$179.20
Purchase #5	$32.46	9.850%	$35.6573	$35.66	$35.65	$35.70
Purchase #6	$139.75	8.662%	$151.8551	$151.86	$151.85	$151.90
Purchase #7	$152.31	4.106%	$158.5638	$158.56	$158.55	$158.60
7 purchase totals =	$1,151.84		$1,256.8334	$1,256.84	$1,256.80	$1,256.90