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	$109.93	8.394%	$119.1575	$119.16	$119.15	$119.20
Purchase #2	$201.69	8.803%	$219.4448	$219.44	$219.45	$219.40
Purchase #3	$36.28	11.251%	$40.3619	$40.36	$40.35	$40.40
Purchase #4	$66.37	7.666%	$71.4579	$71.46	$71.45	$71.50
Purchase #5	$105.84	3.138%	$109.1613	$109.16	$109.15	$109.20
Purchase #6	$242.60	9.763%	$266.285	$266.29	$266.30	$266.30
Purchase #7	$56.87	4.495%	$59.4263	$59.43	$59.45	$59.40
7 purchase totals =	$819.58		$885.2947	$885.30	$885.30	$885.40