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	$157.96	11.660%	$176.3781	$176.38	$176.40	$176.40
Purchase #2	$149.42	11.214%	$166.176	$166.18	$166.20	$166.20
Purchase #3	$48.29	12.140%	$54.1524	$54.15	$54.15	$54.20
Purchase #4	$34.85	6.806%	$37.2219	$37.22	$37.20	$37.20
Purchase #5	$94.47	8.116%	$102.1372	$102.14	$102.15	$102.10
Purchase #6	$81.30	12.137%	$91.1674	$91.17	$91.15	$91.20
Purchase #7	$35.41	6.168%	$37.5941	$37.59	$37.60	$37.60
7 purchase totals =	$601.70		$664.8271	$664.83	$664.85	$664.90