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	$103.38	8.605%	$112.2758	$112.28	$112.30	$112.30
Purchase #2	$101.86	10.557%	$112.6134	$112.61	$112.60	$112.60
Purchase #3	$123.92	5.194%	$130.3564	$130.36	$130.35	$130.40
Purchase #4	$134.87	4.461%	$140.8866	$140.89	$140.90	$140.90
Purchase #5	$215.95	11.241%	$240.2249	$240.22	$240.20	$240.20
Purchase #6	$203.83	11.746%	$227.7719	$227.77	$227.75	$227.80
Purchase #7	$184.59	4.224%	$192.3871	$192.39	$192.40	$192.40
7 purchase totals =	$1,068.40		$1,156.5161	$1,156.52	$1,156.50	$1,156.60