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	$69.26	3.773%	$71.8732	$71.87	$71.85	$71.90
Purchase #2	$141.47	3.382%	$146.2545	$146.25	$146.25	$146.30
Purchase #3	$137.86	4.422%	$143.9562	$143.96	$143.95	$144.00
Purchase #4	$36.29	13.135%	$41.0567	$41.06	$41.05	$41.10
Purchase #5	$146.88	3.471%	$151.9782	$151.98	$152.00	$152.00
Purchase #6	$159.76	5.383%	$168.3599	$168.36	$168.35	$168.40
Purchase #7	$119.50	10.650%	$132.2268	$132.23	$132.25	$132.20
7 purchase totals =	$811.02		$855.7055	$855.71	$855.70	$855.90