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	$196.74	10.123%	$216.656	$216.66	$216.65	$216.70
Purchase #2	$182.46	8.753%	$198.4307	$198.43	$198.45	$198.40
Purchase #3	$133.53	6.727%	$142.5126	$142.51	$142.50	$142.50
Purchase #4	$119.27	6.677%	$127.2337	$127.23	$127.25	$127.20
Purchase #5	$33.51	5.278%	$35.2787	$35.28	$35.30	$35.30
Purchase #6	$138.87	11.815%	$155.2775	$155.28	$155.30	$155.30
Purchase #7	$15.56	10.540%	$17.2	$17.20	$17.20	$17.20
7 purchase totals =	$819.94		$892.5892	$892.59	$892.65	$892.60