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	$177.83	11.861%	$198.9224	$198.92	$198.90	$198.90
Purchase #2	$72.45	7.152%	$77.6316	$77.63	$77.65	$77.60
Purchase #3	$237.61	13.394%	$269.4355	$269.44	$269.45	$269.40
Purchase #4	$91.66	8.734%	$99.6656	$99.67	$99.65	$99.70
Purchase #5	$22.73	8.161%	$24.585	$24.59	$24.60	$24.60
Purchase #6	$67.29	6.670%	$71.7782	$71.78	$71.80	$71.80
Purchase #7	$13.96	13.389%	$15.8291	$15.83	$15.85	$15.80
7 purchase totals =	$683.53		$757.8474	$757.86	$757.90	$757.80