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	$104.36	7.248%	$111.924	$111.92	$111.90	$111.90
Purchase #2	$203.82	8.254%	$220.6433	$220.64	$220.65	$220.60
Purchase #3	$242.74	3.347%	$250.8645	$250.86	$250.85	$250.90
Purchase #4	$117.66	8.435%	$127.5846	$127.58	$127.60	$127.60
Purchase #5	$186.61	13.354%	$211.5299	$211.53	$211.55	$211.50
Purchase #6	$184.53	4.555%	$192.9353	$192.94	$192.95	$192.90
Purchase #7	$176.55	13.250%	$199.9429	$199.94	$199.95	$199.90
7 purchase totals =	$1,216.27		$1,315.4245	$1,315.41	$1,315.45	$1,315.30