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	$146.68	13.487%	$166.4627	$166.46	$166.45	$166.50
Purchase #2	$145.45	3.555%	$150.6207	$150.62	$150.60	$150.60
Purchase #3	$166.44	4.611%	$174.1145	$174.11	$174.10	$174.10
Purchase #4	$220.75	13.469%	$250.4828	$250.48	$250.50	$250.50
Purchase #5	$102.66	3.111%	$105.8538	$105.85	$105.85	$105.90
Purchase #6	$37.67	9.217%	$41.142	$41.14	$41.15	$41.10
Purchase #7	$207.96	5.376%	$219.1399	$219.14	$219.15	$219.10
7 purchase totals =	$1,027.61		$1,107.8164	$1,107.80	$1,107.80	$1,107.80