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	$151.86	11.264%	$168.9655	$168.97	$168.95	$169.00
Purchase #2	$89.93	9.337%	$98.3268	$98.33	$98.35	$98.30
Purchase #3	$245.52	5.829%	$259.8314	$259.83	$259.85	$259.80
Purchase #4	$32.38	8.188%	$35.0313	$35.03	$35.05	$35.00
Purchase #5	$119.74	10.377%	$132.1654	$132.17	$132.15	$132.20
Purchase #6	$186.89	12.424%	$210.1092	$210.11	$210.10	$210.10
Purchase #7	$145.29	13.670%	$165.1511	$165.15	$165.15	$165.20
7 purchase totals =	$971.61		$1,069.5807	$1,069.59	$1,069.60	$1,069.60