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	$146.39	6.839%	$156.4016	$156.40	$156.40	$156.40
Purchase #2	$139.77	6.494%	$148.8467	$148.85	$148.85	$148.80
Purchase #3	$211.84	12.770%	$238.892	$238.89	$238.90	$238.90
Purchase #4	$82.28	10.112%	$90.6002	$90.60	$90.60	$90.60
Purchase #5	$118.35	3.627%	$122.6426	$122.64	$122.65	$122.60
Purchase #6	$99.68	7.772%	$107.4271	$107.43	$107.45	$107.40
Purchase #7	$57.95	7.605%	$62.3571	$62.36	$62.35	$62.40
7 purchase totals =	$856.26		$927.1673	$927.17	$927.20	$927.10