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	$97.65	7.554%	$105.0265	$105.03	$105.05	$105.00
Purchase #2	$104.54	3.351%	$108.0431	$108.04	$108.05	$108.00
Purchase #3	$79.76	12.219%	$89.5059	$89.51	$89.50	$89.50
Purchase #4	$214.26	3.209%	$221.1356	$221.14	$221.15	$221.10
Purchase #5	$40.45	6.525%	$43.0894	$43.09	$43.10	$43.10
Purchase #6	$20.27	11.521%	$22.6053	$22.61	$22.60	$22.60
Purchase #7	$58.31	12.829%	$65.7906	$65.79	$65.80	$65.80
7 purchase totals =	$615.24		$655.1964	$655.21	$655.25	$655.10