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	$39.43	9.597%	$43.2141	$43.21	$43.20	$43.20
Purchase #2	$187.27	13.565%	$212.6732	$212.67	$212.65	$212.70
Purchase #3	$230.31	4.510%	$240.697	$240.70	$240.70	$240.70
Purchase #4	$243.58	4.818%	$255.3157	$255.32	$255.30	$255.30
Purchase #5	$69.53	10.604%	$76.903	$76.90	$76.90	$76.90
Purchase #6	$164.61	4.252%	$171.6092	$171.61	$171.60	$171.60
Purchase #7	$155.95	10.796%	$172.7864	$172.79	$172.80	$172.80
7 purchase totals =	$1,090.68		$1,173.1986	$1,173.20	$1,173.15	$1,173.20