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	$221.42	3.323%	$228.7778	$228.78	$228.80	$228.80
Purchase #2	$180.91	8.370%	$196.0522	$196.05	$196.05	$196.10
Purchase #3	$41.27	12.490%	$46.4246	$46.42	$46.40	$46.40
Purchase #4	$95.72	4.280%	$99.8168	$99.82	$99.80	$99.80
Purchase #5	$216.97	12.716%	$244.5599	$244.56	$244.55	$244.60
Purchase #6	$40.68	7.627%	$43.7827	$43.78	$43.80	$43.80
Purchase #7	$71.30	10.555%	$78.8257	$78.83	$78.85	$78.80
7 purchase totals =	$868.27		$938.2397	$938.24	$938.25	$938.30