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	$227.54	5.572%	$240.2185	$240.22	$240.20	$240.20
Purchase #2	$13.83	6.139%	$14.679	$14.68	$14.70	$14.70
Purchase #3	$5.56	8.208%	$6.0164	$6.02	$6.00	$6.00
Purchase #4	$247.66	3.726%	$256.8878	$256.89	$256.90	$256.90
Purchase #5	$231.84	4.131%	$241.4173	$241.42	$241.40	$241.40
Purchase #6	$203.89	9.805%	$223.8814	$223.88	$223.90	$223.90
Purchase #7	$215.27	6.267%	$228.761	$228.76	$228.75	$228.80
7 purchase totals =	$1,145.59		$1,211.8614	$1,211.87	$1,211.85	$1,211.90