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	$32.40	8.794%	$35.2493	$35.25	$35.25	$35.20
Purchase #2	$122.75	7.133%	$131.5058	$131.51	$131.50	$131.50
Purchase #3	$161.40	10.383%	$178.1582	$178.16	$178.15	$178.20
Purchase #4	$176.44	5.348%	$185.876	$185.88	$185.90	$185.90
Purchase #5	$57.99	4.647%	$60.6848	$60.68	$60.70	$60.70
Purchase #6	$172.72	7.421%	$185.5376	$185.54	$185.55	$185.50
Purchase #7	$10.86	13.560%	$12.3326	$12.33	$12.35	$12.30
7 purchase totals =	$734.56		$789.3443	$789.35	$789.40	$789.30