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	$111.84	11.349%	$124.5327	$124.53	$124.55	$124.50
Purchase #2	$245.96	4.506%	$257.043	$257.04	$257.05	$257.00
Purchase #3	$117.36	7.662%	$126.3521	$126.35	$126.35	$126.40
Purchase #4	$74.36	10.830%	$82.4132	$82.41	$82.40	$82.40
Purchase #5	$127.64	10.657%	$141.2426	$141.24	$141.25	$141.20
Purchase #6	$99.38	10.607%	$109.9212	$109.92	$109.90	$109.90
Purchase #7	$142.94	11.141%	$158.8649	$158.86	$158.85	$158.90
7 purchase totals =	$919.48		$1,000.3697	$1,000.35	$1,000.35	$1,000.30