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	$54.61	3.406%	$56.47	$56.47	$56.45	$56.50
Purchase #2	$54.71	9.330%	$59.8144	$59.81	$59.80	$59.80
Purchase #3	$132.91	10.398%	$146.73	$146.73	$146.75	$146.70
Purchase #4	$34.41	9.116%	$37.5468	$37.55	$37.55	$37.50
Purchase #5	$34.99	10.774%	$38.7598	$38.76	$38.75	$38.80
Purchase #6	$111.75	8.332%	$121.061	$121.06	$121.05	$121.10
Purchase #7	$24.95	3.312%	$25.7763	$25.78	$25.80	$25.80
7 purchase totals =	$448.33		$486.1583	$486.16	$486.15	$486.20