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	$225.64	8.475%	$244.763	$244.76	$244.75	$244.80
Purchase #2	$126.41	13.829%	$143.8912	$143.89	$143.90	$143.90
Purchase #3	$135.61	10.285%	$149.5575	$149.56	$149.55	$149.60
Purchase #4	$89.31	3.376%	$92.3251	$92.33	$92.35	$92.30
Purchase #5	$55.76	11.143%	$61.9733	$61.97	$61.95	$62.00
Purchase #6	$19.69	3.691%	$20.4168	$20.42	$20.40	$20.40
Purchase #7	$178.63	10.159%	$196.777	$196.78	$196.80	$196.80
7 purchase totals =	$831.05		$909.7039	$909.71	$909.70	$909.80