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	$176.87	7.712%	$190.5102	$190.51	$190.50	$190.50
Purchase #2	$175.69	5.738%	$185.7711	$185.77	$185.75	$185.80
Purchase #3	$64.97	11.522%	$72.4558	$72.46	$72.45	$72.50
Purchase #4	$16.26	4.120%	$16.9299	$16.93	$16.95	$16.90
Purchase #5	$100.81	5.316%	$106.1691	$106.17	$106.15	$106.20
Purchase #6	$77.96	5.721%	$82.4201	$82.42	$82.40	$82.40
Purchase #7	$35.50	12.455%	$39.9215	$39.92	$39.90	$39.90
7 purchase totals =	$648.06		$694.1777	$694.18	$694.10	$694.20