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	$78.76	5.319%	$82.9492	$82.95	$82.95	$82.90
Purchase #2	$81.52	11.137%	$90.5989	$90.60	$90.60	$90.60
Purchase #3	$72.60	3.721%	$75.3014	$75.30	$75.30	$75.30
Purchase #4	$35.26	10.201%	$38.8569	$38.86	$38.85	$38.90
Purchase #5	$74.79	6.290%	$79.4943	$79.49	$79.50	$79.50
Purchase #6	$151.26	6.168%	$160.5897	$160.59	$160.60	$160.60
Purchase #7	$207.94	3.348%	$214.9018	$214.90	$214.90	$214.90
7 purchase totals =	$702.13		$742.6922	$742.69	$742.70	$742.70