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	$151.28	11.663%	$168.9238	$168.92	$168.90	$168.90
Purchase #2	$126.56	3.420%	$130.8884	$130.89	$130.90	$130.90
Purchase #3	$183.95	4.250%	$191.7679	$191.77	$191.75	$191.80
Purchase #4	$51.41	7.741%	$55.3896	$55.39	$55.40	$55.40
Purchase #5	$141.60	5.609%	$149.5423	$149.54	$149.55	$149.50
Purchase #6	$199.91	13.204%	$226.3061	$226.31	$226.30	$226.30
Purchase #7	$74.51	5.378%	$78.5171	$78.52	$78.50	$78.50
7 purchase totals =	$929.22		$1,001.3352	$1,001.34	$1,001.30	$1,001.30