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	$59.42	4.408%	$62.0392	$62.04	$62.05	$62.00
Purchase #2	$118.75	7.510%	$127.6681	$127.67	$127.65	$127.70
Purchase #3	$136.71	8.505%	$148.3372	$148.34	$148.35	$148.30
Purchase #4	$180.42	7.593%	$194.1193	$194.12	$194.10	$194.10
Purchase #5	$84.37	5.606%	$89.0998	$89.10	$89.10	$89.10
Purchase #6	$103.70	5.712%	$109.6233	$109.62	$109.60	$109.60
Purchase #7	$99.97	7.488%	$107.4558	$107.46	$107.45	$107.50
7 purchase totals =	$783.34		$838.3427	$838.35	$838.30	$838.30