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	$234.49	8.423%	$254.2411	$254.24	$254.25	$254.20
Purchase #2	$52.89	3.671%	$54.8316	$54.83	$54.85	$54.80
Purchase #3	$182.25	4.390%	$190.2508	$190.25	$190.25	$190.30
Purchase #4	$11.48	9.529%	$12.5739	$12.57	$12.55	$12.60
Purchase #5	$18.87	3.231%	$19.4797	$19.48	$19.50	$19.50
Purchase #6	$221.96	11.405%	$247.2745	$247.27	$247.25	$247.30
Purchase #7	$174.91	6.610%	$186.4716	$186.47	$186.45	$186.50
7 purchase totals =	$896.85		$965.1232	$965.11	$965.10	$965.20