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	$226.58	13.413%	$256.9712	$256.97	$256.95	$257.00
Purchase #2	$6.55	7.710%	$7.055	$7.06	$7.05	$7.10
Purchase #3	$223.77	9.451%	$244.9185	$244.92	$244.90	$244.90
Purchase #4	$85.32	5.631%	$90.1244	$90.12	$90.10	$90.10
Purchase #5	$151.26	5.629%	$159.7744	$159.77	$159.75	$159.80
Purchase #6	$211.66	13.195%	$239.5885	$239.59	$239.60	$239.60
Purchase #7	$19.65	11.353%	$21.8809	$21.88	$21.90	$21.90
7 purchase totals =	$924.79		$1,020.3129	$1,020.31	$1,020.25	$1,020.40