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	$33.55	3.842%	$34.839	$34.84	$34.85	$34.80
Purchase #2	$126.41	4.310%	$131.8583	$131.86	$131.85	$131.90
Purchase #3	$27.58	4.447%	$28.8065	$28.81	$28.80	$28.80
Purchase #4	$114.60	11.116%	$127.3389	$127.34	$127.35	$127.30
Purchase #5	$65.26	13.404%	$74.0075	$74.01	$74.00	$74.00
Purchase #6	$100.62	5.536%	$106.1903	$106.19	$106.20	$106.20
Purchase #7	$205.89	8.489%	$223.368	$223.37	$223.35	$223.40
7 purchase totals =	$673.91		$726.4085	$726.42	$726.40	$726.40