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	$158.44	4.714%	$165.9089	$165.91	$165.90	$165.90
Purchase #2	$174.56	12.350%	$196.1182	$196.12	$196.10	$196.10
Purchase #3	$100.73	4.756%	$105.5207	$105.52	$105.50	$105.50
Purchase #4	$19.95	5.418%	$21.0309	$21.03	$21.05	$21.00
Purchase #5	$8.60	4.159%	$8.9577	$8.96	$8.95	$9.00
Purchase #6	$82.61	4.387%	$86.2341	$86.23	$86.25	$86.20
Purchase #7	$241.90	12.658%	$272.5197	$272.52	$272.50	$272.50
7 purchase totals =	$786.79		$856.2902	$856.29	$856.25	$856.20