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	$161.90	6.802%	$172.9124	$172.91	$172.90	$172.90
Purchase #2	$10.66	6.214%	$11.3224	$11.32	$11.30	$11.30
Purchase #3	$183.31	6.845%	$195.8576	$195.86	$195.85	$195.90
Purchase #4	$62.94	7.505%	$67.6636	$67.66	$67.65	$67.70
Purchase #5	$236.82	7.719%	$255.1001	$255.10	$255.10	$255.10
Purchase #6	$103.65	5.779%	$109.6399	$109.64	$109.65	$109.60
Purchase #7	$77.54	9.717%	$85.0746	$85.07	$85.05	$85.10
7 purchase totals =	$836.82		$897.5706	$897.56	$897.50	$897.60