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	$98.88	12.641%	$111.3794	$111.38	$111.40	$111.40
Purchase #2	$162.64	8.200%	$175.9765	$175.98	$176.00	$176.00
Purchase #3	$17.72	12.621%	$19.9564	$19.96	$19.95	$20.00
Purchase #4	$248.87	6.336%	$264.6384	$264.64	$264.65	$264.60
Purchase #5	$186.34	3.847%	$193.5085	$193.51	$193.50	$193.50
Purchase #6	$30.69	6.299%	$32.6232	$32.62	$32.60	$32.60
Purchase #7	$101.59	10.559%	$112.3169	$112.32	$112.30	$112.30
7 purchase totals =	$846.73		$910.3993	$910.41	$910.40	$910.40