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	$50.68	7.440%	$54.4506	$54.45	$54.45	$54.50
Purchase #2	$27.92	6.204%	$29.6522	$29.65	$29.65	$29.70
Purchase #3	$215.89	11.609%	$240.9527	$240.95	$240.95	$241.00
Purchase #4	$160.55	4.492%	$167.7619	$167.76	$167.75	$167.80
Purchase #5	$118.39	11.117%	$131.5514	$131.55	$131.55	$131.60
Purchase #6	$165.39	13.283%	$187.3588	$187.36	$187.35	$187.40
Purchase #7	$215.43	12.690%	$242.7681	$242.77	$242.75	$242.80
7 purchase totals =	$954.25		$1,054.4957	$1,054.49	$1,054.45	$1,054.80