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	$61.49	10.830%	$68.1494	$68.15	$68.15	$68.10
Purchase #2	$115.62	7.183%	$123.925	$123.93	$123.95	$123.90
Purchase #3	$126.57	8.211%	$136.9627	$136.96	$136.95	$137.00
Purchase #4	$9.76	7.639%	$10.5056	$10.51	$10.50	$10.50
Purchase #5	$185.31	13.685%	$210.6697	$210.67	$210.65	$210.70
Purchase #6	$80.85	11.601%	$90.2294	$90.23	$90.25	$90.20
Purchase #7	$52.38	12.702%	$59.0333	$59.03	$59.05	$59.00
7 purchase totals =	$631.98		$699.4751	$699.48	$699.50	$699.40