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	$91.76	11.742%	$102.5345	$102.53	$102.55	$102.50
Purchase #2	$121.91	5.502%	$128.6175	$128.62	$128.60	$128.60
Purchase #3	$51.52	6.702%	$54.9729	$54.97	$54.95	$55.00
Purchase #4	$102.85	13.272%	$116.5003	$116.50	$116.50	$116.50
Purchase #5	$18.49	11.727%	$20.6583	$20.66	$20.65	$20.70
Purchase #6	$98.84	10.569%	$109.2864	$109.29	$109.30	$109.30
Purchase #7	$176.89	13.133%	$200.121	$200.12	$200.10	$200.10
7 purchase totals =	$662.26		$732.6909	$732.69	$732.65	$732.70