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	$198.94	12.435%	$223.6782	$223.68	$223.70	$223.70
Purchase #2	$150.57	13.184%	$170.4211	$170.42	$170.40	$170.40
Purchase #3	$60.47	3.565%	$62.6258	$62.63	$62.65	$62.60
Purchase #4	$208.68	4.280%	$217.6115	$217.61	$217.60	$217.60
Purchase #5	$226.59	12.464%	$254.8322	$254.83	$254.85	$254.80
Purchase #6	$188.49	4.131%	$196.2765	$196.28	$196.30	$196.30
Purchase #7	$153.48	11.655%	$171.3681	$171.37	$171.35	$171.40
7 purchase totals =	$1,187.22		$1,296.8134	$1,296.82	$1,296.85	$1,296.80