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	$170.38	10.612%	$188.4607	$188.46	$188.45	$188.50
Purchase #2	$85.33	10.573%	$94.3519	$94.35	$94.35	$94.40
Purchase #3	$126.80	11.556%	$141.453	$141.45	$141.45	$141.50
Purchase #4	$226.43	12.689%	$255.1617	$255.16	$255.15	$255.20
Purchase #5	$134.83	5.268%	$141.9328	$141.93	$141.95	$141.90
Purchase #6	$9.39	11.772%	$10.4954	$10.50	$10.50	$10.50
Purchase #7	$166.70	11.811%	$186.3889	$186.39	$186.40	$186.40
7 purchase totals =	$919.86		$1,018.2444	$1,018.24	$1,018.25	$1,018.40