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	$99.97	11.355%	$111.3216	$111.32	$111.30	$111.30
Purchase #2	$132.55	5.123%	$139.3405	$139.34	$139.35	$139.30
Purchase #3	$167.58	3.470%	$173.395	$173.40	$173.40	$173.40
Purchase #4	$186.36	5.255%	$196.1532	$196.15	$196.15	$196.20
Purchase #5	$247.53	13.191%	$280.1817	$280.18	$280.20	$280.20
Purchase #6	$89.28	3.830%	$92.6994	$92.70	$92.70	$92.70
Purchase #7	$52.31	3.288%	$54.03	$54.03	$54.05	$54.00
7 purchase totals =	$975.58		$1,047.1214	$1,047.12	$1,047.15	$1,047.10