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	$101.56	3.579%	$105.1948	$105.19	$105.20	$105.20
Purchase #2	$176.56	8.756%	$192.0196	$192.02	$192.00	$192.00
Purchase #3	$89.90	8.232%	$97.3006	$97.30	$97.30	$97.30
Purchase #4	$102.31	6.634%	$109.0972	$109.10	$109.10	$109.10
Purchase #5	$125.69	4.388%	$131.2053	$131.21	$131.20	$131.20
Purchase #6	$152.25	12.184%	$170.8001	$170.80	$170.80	$170.80
Purchase #7	$233.26	9.747%	$255.9959	$256.00	$256.00	$256.00
7 purchase totals =	$981.53		$1,061.6135	$1,061.62	$1,061.60	$1,061.60