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	$165.61	11.719%	$185.0178	$185.02	$185.00	$185.00
Purchase #2	$220.85	8.473%	$239.5626	$239.56	$239.55	$239.60
Purchase #3	$176.38	5.111%	$185.3948	$185.39	$185.40	$185.40
Purchase #4	$100.57	10.166%	$110.7939	$110.79	$110.80	$110.80
Purchase #5	$249.81	11.655%	$278.9254	$278.93	$278.95	$278.90
Purchase #6	$139.55	13.670%	$158.6265	$158.63	$158.65	$158.60
Purchase #7	$74.30	12.105%	$83.294	$83.29	$83.30	$83.30
7 purchase totals =	$1,127.07		$1,241.6150	$1,241.61	$1,241.65	$1,241.60