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	$83.28	8.776%	$90.5887	$90.59	$90.60	$90.60
Purchase #2	$89.71	12.273%	$100.7201	$100.72	$100.70	$100.70
Purchase #3	$233.31	11.339%	$259.765	$259.77	$259.75	$259.80
Purchase #4	$14.92	3.420%	$15.4303	$15.43	$15.45	$15.40
Purchase #5	$128.27	6.353%	$136.419	$136.42	$136.40	$136.40
Purchase #6	$173.81	3.589%	$180.048	$180.05	$180.05	$180.00
Purchase #7	$233.93	4.110%	$243.5445	$243.54	$243.55	$243.50
7 purchase totals =	$957.23		$1,026.5156	$1,026.52	$1,026.50	$1,026.40