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	$187.74	13.373%	$212.8465	$212.85	$212.85	$212.80
Purchase #2	$116.41	12.447%	$130.8996	$130.90	$130.90	$130.90
Purchase #3	$91.47	9.477%	$100.1386	$100.14	$100.15	$100.10
Purchase #4	$29.94	11.517%	$33.3882	$33.39	$33.40	$33.40
Purchase #5	$242.57	5.395%	$255.6567	$255.66	$255.65	$255.70
Purchase #6	$35.59	10.765%	$39.4213	$39.42	$39.40	$39.40
Purchase #7	$180.49	5.747%	$190.8628	$190.86	$190.85	$190.90
7 purchase totals =	$884.21		$963.2137	$963.22	$963.20	$963.20