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	$141.45	8.604%	$153.6204	$153.62	$153.60	$153.60
Purchase #2	$142.63	6.136%	$151.3818	$151.38	$151.40	$151.40
Purchase #3	$72.53	5.645%	$76.6243	$76.62	$76.60	$76.60
Purchase #4	$170.78	4.257%	$178.0501	$178.05	$178.05	$178.10
Purchase #5	$5.62	11.699%	$6.2775	$6.28	$6.30	$6.30
Purchase #6	$230.59	9.114%	$251.606	$251.61	$251.60	$251.60
Purchase #7	$56.98	5.196%	$59.9407	$59.94	$59.95	$59.90
7 purchase totals =	$820.58		$877.5008	$877.50	$877.50	$877.50