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	$162.79	5.590%	$171.89	$171.89	$171.90	$171.90
Purchase #2	$19.34	3.680%	$20.0517	$20.05	$20.05	$20.10
Purchase #3	$134.60	5.251%	$141.6678	$141.67	$141.65	$141.70
Purchase #4	$138.26	7.542%	$148.6876	$148.69	$148.70	$148.70
Purchase #5	$233.83	13.389%	$265.1375	$265.14	$265.15	$265.10
Purchase #6	$98.33	11.382%	$109.5219	$109.52	$109.50	$109.50
Purchase #7	$233.91	3.191%	$241.3741	$241.37	$241.35	$241.40
7 purchase totals =	$1,021.06		$1,098.3306	$1,098.33	$1,098.30	$1,098.40