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	$81.35	4.792%	$85.2483	$85.25	$85.25	$85.20
Purchase #2	$89.40	6.440%	$95.1574	$95.16	$95.15	$95.20
Purchase #3	$153.88	5.697%	$162.6465	$162.65	$162.65	$162.60
Purchase #4	$168.99	5.696%	$178.6157	$178.62	$178.60	$178.60
Purchase #5	$11.94	4.741%	$12.5061	$12.51	$12.50	$12.50
Purchase #6	$60.44	12.399%	$67.934	$67.93	$67.95	$67.90
Purchase #7	$7.29	3.600%	$7.5524	$7.55	$7.55	$7.60
7 purchase totals =	$573.29		$609.6604	$609.67	$609.65	$609.60