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	$182.83	6.562%	$194.8273	$194.83	$194.85	$194.80
Purchase #2	$131.29	4.813%	$137.609	$137.61	$137.60	$137.60
Purchase #3	$101.97	9.657%	$111.8172	$111.82	$111.80	$111.80
Purchase #4	$201.71	4.637%	$211.0633	$211.06	$211.05	$211.10
Purchase #5	$94.37	5.722%	$99.7699	$99.77	$99.75	$99.80
Purchase #6	$213.61	5.776%	$225.9481	$225.95	$225.95	$225.90
Purchase #7	$82.27	10.440%	$90.859	$90.86	$90.85	$90.90
7 purchase totals =	$1,008.05		$1,071.8938	$1,071.90	$1,071.85	$1,071.90