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	$250.32	3.399%	$258.8284	$258.83	$258.85	$258.80
Purchase #2	$88.34	12.619%	$99.4876	$99.49	$99.50	$99.50
Purchase #3	$225.42	13.576%	$256.023	$256.02	$256.00	$256.00
Purchase #4	$112.55	13.532%	$127.7803	$127.78	$127.80	$127.80
Purchase #5	$33.52	13.638%	$38.0915	$38.09	$38.10	$38.10
Purchase #6	$30.55	10.569%	$33.7788	$33.78	$33.80	$33.80
Purchase #7	$226.70	5.129%	$238.3274	$238.33	$238.35	$238.30
7 purchase totals =	$967.40		$1,052.3170	$1,052.32	$1,052.40	$1,052.30