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	$133.78	6.656%	$142.6844	$142.68	$142.70	$142.70
Purchase #2	$188.52	7.317%	$202.314	$202.31	$202.30	$202.30
Purchase #3	$222.41	7.203%	$238.4302	$238.43	$238.45	$238.40
Purchase #4	$9.80	13.689%	$11.1415	$11.14	$11.15	$11.10
Purchase #5	$78.92	4.269%	$82.2891	$82.29	$82.30	$82.30
Purchase #6	$238.53	6.824%	$254.8073	$254.81	$254.80	$254.80
Purchase #7	$141.70	6.519%	$150.9374	$150.94	$150.95	$150.90
7 purchase totals =	$1,013.66		$1,082.6039	$1,082.60	$1,082.65	$1,082.50