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	$135.65	11.689%	$151.5061	$151.51	$151.50	$151.50
Purchase #2	$69.57	12.705%	$78.4089	$78.41	$78.40	$78.40
Purchase #3	$66.57	10.796%	$73.7569	$73.76	$73.75	$73.80
Purchase #4	$162.45	6.385%	$172.8224	$172.82	$172.80	$172.80
Purchase #5	$43.49	11.112%	$48.3226	$48.32	$48.30	$48.30
Purchase #6	$129.42	10.842%	$143.4517	$143.45	$143.45	$143.50
Purchase #7	$112.82	3.721%	$117.018	$117.02	$117.00	$117.00
7 purchase totals =	$719.97		$785.2866	$785.29	$785.20	$785.30