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	$197.29	10.617%	$218.2363	$218.24	$218.25	$218.20
Purchase #2	$144.96	11.382%	$161.4593	$161.46	$161.45	$161.50
Purchase #3	$111.25	6.138%	$118.0785	$118.08	$118.10	$118.10
Purchase #4	$38.53	11.692%	$43.0349	$43.03	$43.05	$43.00
Purchase #5	$80.75	9.700%	$88.5828	$88.58	$88.60	$88.60
Purchase #6	$153.31	5.187%	$161.2622	$161.26	$161.25	$161.30
Purchase #7	$165.46	13.709%	$188.1429	$188.14	$188.15	$188.10
7 purchase totals =	$891.55		$978.7969	$978.79	$978.85	$978.80