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	$159.82	9.252%	$174.6065	$174.61	$174.60	$174.60
Purchase #2	$142.56	8.452%	$154.6092	$154.61	$154.60	$154.60
Purchase #3	$179.37	8.644%	$194.8747	$194.87	$194.85	$194.90
Purchase #4	$209.47	3.410%	$216.6129	$216.61	$216.60	$216.60
Purchase #5	$88.37	12.209%	$99.1591	$99.16	$99.15	$99.20
Purchase #6	$121.55	5.345%	$128.0468	$128.05	$128.05	$128.00
Purchase #7	$215.66	10.575%	$238.466	$238.47	$238.45	$238.50
7 purchase totals =	$1,116.80		$1,206.3752	$1,206.38	$1,206.30	$1,206.40