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	$244.58	7.338%	$262.5273	$262.53	$262.55	$262.50
Purchase #2	$134.52	7.112%	$144.0871	$144.09	$144.10	$144.10
Purchase #3	$127.33	9.334%	$139.215	$139.22	$139.20	$139.20
Purchase #4	$30.57	5.320%	$32.1963	$32.20	$32.20	$32.20
Purchase #5	$110.34	7.429%	$118.5372	$118.54	$118.55	$118.50
Purchase #6	$184.78	9.691%	$202.687	$202.69	$202.70	$202.70
Purchase #7	$161.98	6.384%	$172.3208	$172.32	$172.30	$172.30
7 purchase totals =	$994.10		$1,071.5707	$1,071.59	$1,071.60	$1,071.50