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	$169.45	13.597%	$192.4901	$192.49	$192.50	$192.50
Purchase #2	$72.47	11.424%	$80.749	$80.75	$80.75	$80.70
Purchase #3	$193.67	13.382%	$219.5869	$219.59	$219.60	$219.60
Purchase #4	$155.40	4.818%	$162.8872	$162.89	$162.90	$162.90
Purchase #5	$39.79	7.324%	$42.7042	$42.70	$42.70	$42.70
Purchase #6	$127.79	5.498%	$134.8159	$134.82	$134.80	$134.80
Purchase #7	$51.67	5.303%	$54.4101	$54.41	$54.40	$54.40
7 purchase totals =	$810.24		$887.6434	$887.65	$887.65	$887.60