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	$85.28	4.613%	$89.214	$89.21	$89.20	$89.20
Purchase #2	$105.48	9.271%	$115.2591	$115.26	$115.25	$115.30
Purchase #3	$18.82	3.572%	$19.4923	$19.49	$19.50	$19.50
Purchase #4	$132.25	8.503%	$143.4952	$143.50	$143.50	$143.50
Purchase #5	$56.72	9.409%	$62.0568	$62.06	$62.05	$62.10
Purchase #6	$109.33	9.446%	$119.6573	$119.66	$119.65	$119.70
Purchase #7	$10.88	10.134%	$11.9826	$11.98	$12.00	$12.00
7 purchase totals =	$518.76		$561.1573	$561.16	$561.15	$561.30