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	$106.83	3.813%	$110.9034	$110.90	$110.90	$110.90
Purchase #2	$136.42	13.524%	$154.8694	$154.87	$154.85	$154.90
Purchase #3	$185.47	10.294%	$204.5623	$204.56	$204.55	$204.60
Purchase #4	$38.27	5.544%	$40.3917	$40.39	$40.40	$40.40
Purchase #5	$29.68	4.485%	$31.0111	$31.01	$31.00	$31.00
Purchase #6	$77.26	4.747%	$80.9275	$80.93	$80.95	$80.90
Purchase #7	$127.50	3.253%	$131.6476	$131.65	$131.65	$131.60
7 purchase totals =	$701.43		$754.3130	$754.31	$754.30	$754.30