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	$107.65	3.160%	$111.0517	$111.05	$111.05	$111.10
Purchase #2	$85.66	4.788%	$89.7614	$89.76	$89.75	$89.80
Purchase #3	$77.66	10.507%	$85.8197	$85.82	$85.80	$85.80
Purchase #4	$28.59	10.228%	$31.5142	$31.51	$31.50	$31.50
Purchase #5	$206.63	8.586%	$224.3713	$224.37	$224.35	$224.40
Purchase #6	$52.88	3.671%	$54.8212	$54.82	$54.80	$54.80
Purchase #7	$27.70	12.686%	$31.214	$31.21	$31.20	$31.20
7 purchase totals =	$586.77		$628.5535	$628.54	$628.45	$628.60