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	$56.59	7.518%	$60.8444	$60.84	$60.85	$60.80
Purchase #2	$118.49	7.394%	$127.2512	$127.25	$127.25	$127.30
Purchase #3	$109.47	6.420%	$116.498	$116.50	$116.50	$116.50
Purchase #4	$58.34	12.393%	$65.5701	$65.57	$65.55	$65.60
Purchase #5	$77.87	12.442%	$87.5586	$87.56	$87.55	$87.60
Purchase #6	$248.46	6.501%	$264.6124	$264.61	$264.60	$264.60
Purchase #7	$247.48	9.682%	$271.441	$271.44	$271.45	$271.40
7 purchase totals =	$916.70		$993.7757	$993.77	$993.75	$993.80