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	$174.54	12.306%	$196.0189	$196.02	$196.00	$196.00
Purchase #2	$219.92	5.165%	$231.2789	$231.28	$231.30	$231.30
Purchase #3	$139.63	3.634%	$144.7042	$144.70	$144.70	$144.70
Purchase #4	$121.30	5.208%	$127.6173	$127.62	$127.60	$127.60
Purchase #5	$150.27	5.461%	$158.4762	$158.48	$158.50	$158.50
Purchase #6	$160.69	4.309%	$167.6141	$167.61	$167.60	$167.60
Purchase #7	$110.75	4.384%	$115.6053	$115.61	$115.60	$115.60
7 purchase totals =	$1,077.10		$1,141.3149	$1,141.32	$1,141.30	$1,141.30