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	$171.39	11.666%	$191.3844	$191.38	$191.40	$191.40
Purchase #2	$215.35	7.165%	$230.7798	$230.78	$230.80	$230.80
Purchase #3	$197.52	11.109%	$219.4625	$219.46	$219.45	$219.50
Purchase #4	$101.72	5.776%	$107.5953	$107.60	$107.60	$107.60
Purchase #5	$63.30	8.658%	$68.7805	$68.78	$68.80	$68.80
Purchase #6	$87.45	3.123%	$90.1811	$90.18	$90.20	$90.20
Purchase #7	$169.38	11.232%	$188.4048	$188.40	$188.40	$188.40
7 purchase totals =	$1,006.11		$1,096.5884	$1,096.58	$1,096.65	$1,096.70