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	$180.28	9.856%	$198.0484	$198.05	$198.05	$198.00
Purchase #2	$85.32	10.303%	$94.1105	$94.11	$94.10	$94.10
Purchase #3	$57.33	6.856%	$61.2605	$61.26	$61.25	$61.30
Purchase #4	$10.60	5.196%	$11.1508	$11.15	$11.15	$11.20
Purchase #5	$150.72	5.653%	$159.2402	$159.24	$159.25	$159.20
Purchase #6	$201.91	10.532%	$223.1752	$223.18	$223.20	$223.20
Purchase #7	$242.32	5.452%	$255.5313	$255.53	$255.55	$255.50
7 purchase totals =	$928.48		$1,002.5169	$1,002.52	$1,002.55	$1,002.50