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	$63.64	13.835%	$72.4446	$72.44	$72.45	$72.40
Purchase #2	$93.95	12.318%	$105.5228	$105.52	$105.50	$105.50
Purchase #3	$69.61	11.692%	$77.7488	$77.75	$77.75	$77.70
Purchase #4	$219.54	10.340%	$242.2404	$242.24	$242.25	$242.20
Purchase #5	$225.89	7.707%	$243.2993	$243.30	$243.30	$243.30
Purchase #6	$235.75	8.245%	$255.1876	$255.19	$255.20	$255.20
Purchase #7	$141.58	3.554%	$146.6118	$146.61	$146.60	$146.60
7 purchase totals =	$1,049.96		$1,143.0553	$1,143.05	$1,143.05	$1,142.90