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	$66.86	6.704%	$71.3423	$71.34	$71.35	$71.30
Purchase #2	$125.26	5.485%	$132.1305	$132.13	$132.15	$132.10
Purchase #3	$110.99	11.412%	$123.6562	$123.66	$123.65	$123.70
Purchase #4	$225.31	9.769%	$247.3205	$247.32	$247.30	$247.30
Purchase #5	$97.90	11.366%	$109.0273	$109.03	$109.05	$109.00
Purchase #6	$106.31	11.406%	$118.4357	$118.44	$118.45	$118.40
Purchase #7	$59.68	11.381%	$66.4722	$66.47	$66.45	$66.50
7 purchase totals =	$792.31		$868.3847	$868.39	$868.40	$868.30