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	$118.85	7.125%	$127.3181	$127.32	$127.30	$127.30
Purchase #2	$47.89	3.319%	$49.4795	$49.48	$49.50	$49.50
Purchase #3	$50.99	10.677%	$56.4342	$56.43	$56.45	$56.40
Purchase #4	$64.27	4.124%	$66.9205	$66.92	$66.90	$66.90
Purchase #5	$13.77	7.454%	$14.7964	$14.80	$14.80	$14.80
Purchase #6	$30.98	4.179%	$32.2747	$32.27	$32.25	$32.30
Purchase #7	$130.26	10.629%	$144.1053	$144.11	$144.10	$144.10
7 purchase totals =	$457.01		$491.3287	$491.33	$491.30	$491.30