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	$212.71	3.572%	$220.308	$220.31	$220.30	$220.30
Purchase #2	$38.92	7.468%	$41.8265	$41.83	$41.85	$41.80
Purchase #3	$124.50	5.253%	$131.04	$131.04	$131.05	$131.00
Purchase #4	$158.80	8.213%	$171.8422	$171.84	$171.85	$171.80
Purchase #5	$19.91	13.728%	$22.6432	$22.64	$22.65	$22.60
Purchase #6	$25.60	13.793%	$29.131	$29.13	$29.15	$29.10
Purchase #7	$101.36	9.829%	$111.3227	$111.32	$111.30	$111.30
7 purchase totals =	$681.80		$728.1136	$728.11	$728.15	$727.90