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	$237.90	3.259%	$245.6532	$245.65	$245.65	$245.70
Purchase #2	$49.86	8.160%	$53.9286	$53.93	$53.95	$53.90
Purchase #3	$34.33	10.289%	$37.8622	$37.86	$37.85	$37.90
Purchase #4	$55.27	9.391%	$60.4604	$60.46	$60.45	$60.50
Purchase #5	$168.47	11.641%	$188.0816	$188.08	$188.10	$188.10
Purchase #6	$91.38	8.545%	$99.1884	$99.19	$99.20	$99.20
Purchase #7	$49.60	5.594%	$52.3746	$52.37	$52.35	$52.40
7 purchase totals =	$686.81		$737.5490	$737.54	$737.55	$737.70