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	$78.37	13.869%	$89.2391	$89.24	$89.25	$89.20
Purchase #2	$117.76	8.497%	$127.7661	$127.77	$127.75	$127.80
Purchase #3	$36.25	9.430%	$39.6684	$39.67	$39.65	$39.70
Purchase #4	$211.61	4.128%	$220.3453	$220.35	$220.35	$220.30
Purchase #5	$47.58	12.766%	$53.6541	$53.65	$53.65	$53.70
Purchase #6	$54.89	9.496%	$60.1024	$60.10	$60.10	$60.10
Purchase #7	$140.59	3.330%	$145.2716	$145.27	$145.25	$145.30
7 purchase totals =	$687.05		$736.0470	$736.05	$736.00	$736.10