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	$164.79	12.366%	$185.1679	$185.17	$185.15	$185.20
Purchase #2	$151.83	8.491%	$164.7219	$164.72	$164.70	$164.70
Purchase #3	$202.31	13.548%	$229.719	$229.72	$229.70	$229.70
Purchase #4	$243.38	13.218%	$275.55	$275.55	$275.55	$275.60
Purchase #5	$184.95	7.556%	$198.9248	$198.92	$198.90	$198.90
Purchase #6	$123.89	12.539%	$139.4246	$139.42	$139.40	$139.40
Purchase #7	$147.26	13.176%	$166.663	$166.66	$166.65	$166.70
7 purchase totals =	$1,218.41		$1,360.1712	$1,360.16	$1,360.05	$1,360.20