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	$159.71	8.254%	$172.8925	$172.89	$172.90	$172.90
Purchase #2	$10.96	5.373%	$11.5489	$11.55	$11.55	$11.50
Purchase #3	$211.62	12.112%	$237.2514	$237.25	$237.25	$237.30
Purchase #4	$151.78	9.233%	$165.7938	$165.79	$165.80	$165.80
Purchase #5	$211.54	13.733%	$240.5908	$240.59	$240.60	$240.60
Purchase #6	$51.80	10.659%	$57.3214	$57.32	$57.30	$57.30
Purchase #7	$146.36	10.534%	$161.7776	$161.78	$161.80	$161.80
7 purchase totals =	$943.77		$1,047.1764	$1,047.17	$1,047.20	$1,047.20