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	$108.77	13.248%	$123.1798	$123.18	$123.20	$123.20
Purchase #2	$210.32	13.215%	$238.1138	$238.11	$238.10	$238.10
Purchase #3	$28.68	10.347%	$31.6475	$31.65	$31.65	$31.60
Purchase #4	$17.54	11.333%	$19.5278	$19.53	$19.55	$19.50
Purchase #5	$141.78	4.850%	$148.6563	$148.66	$148.65	$148.70
Purchase #6	$188.40	6.205%	$200.0902	$200.09	$200.10	$200.10
Purchase #7	$242.39	4.611%	$253.5666	$253.57	$253.55	$253.60
7 purchase totals =	$937.88		$1,014.7820	$1,014.79	$1,014.80	$1,014.80