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	$215.86	3.413%	$223.2273	$223.23	$223.25	$223.20
Purchase #2	$85.29	5.328%	$89.8343	$89.83	$89.85	$89.80
Purchase #3	$28.55	10.258%	$31.4787	$31.48	$31.50	$31.50
Purchase #4	$155.62	9.435%	$170.3027	$170.30	$170.30	$170.30
Purchase #5	$67.95	12.710%	$76.5864	$76.59	$76.60	$76.60
Purchase #6	$69.53	11.147%	$77.2805	$77.28	$77.30	$77.30
Purchase #7	$45.40	9.129%	$49.5446	$49.54	$49.55	$49.50
7 purchase totals =	$668.20		$718.2545	$718.25	$718.35	$718.20