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	$23.59	11.467%	$26.2951	$26.30	$26.30	$26.30
Purchase #2	$114.73	10.839%	$127.1656	$127.17	$127.15	$127.20
Purchase #3	$179.51	10.237%	$197.8864	$197.89	$197.90	$197.90
Purchase #4	$217.80	13.372%	$246.9242	$246.92	$246.90	$246.90
Purchase #5	$153.26	12.134%	$171.8566	$171.86	$171.85	$171.90
Purchase #6	$92.90	7.596%	$99.9567	$99.96	$99.95	$100.00
Purchase #7	$179.28	9.652%	$196.5841	$196.58	$196.60	$196.60
7 purchase totals =	$961.07		$1,066.6687	$1,066.68	$1,066.65	$1,066.80