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	$165.86	8.251%	$179.5451	$179.55	$179.55	$179.50
Purchase #2	$173.50	7.173%	$185.9452	$185.95	$185.95	$185.90
Purchase #3	$30.49	10.536%	$33.7024	$33.70	$33.70	$33.70
Purchase #4	$125.99	4.210%	$131.2942	$131.29	$131.30	$131.30
Purchase #5	$236.86	13.536%	$268.9214	$268.92	$268.90	$268.90
Purchase #6	$112.44	13.536%	$127.6599	$127.66	$127.65	$127.70
Purchase #7	$73.43	13.551%	$83.3805	$83.38	$83.40	$83.40
7 purchase totals =	$918.57		$1,010.4487	$1,010.45	$1,010.45	$1,010.40