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	$111.93	8.414%	$121.3478	$121.35	$121.35	$121.30
Purchase #2	$29.96	5.369%	$31.5686	$31.57	$31.55	$31.60
Purchase #3	$94.55	11.353%	$105.2843	$105.28	$105.30	$105.30
Purchase #4	$160.34	4.229%	$167.1208	$167.12	$167.10	$167.10
Purchase #5	$49.34	10.397%	$54.4699	$54.47	$54.45	$54.50
Purchase #6	$166.89	10.559%	$184.5119	$184.51	$184.50	$184.50
Purchase #7	$213.52	3.810%	$221.6551	$221.66	$221.65	$221.70
7 purchase totals =	$826.53		$885.9584	$885.96	$885.90	$886.00