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	$58.35	5.688%	$61.6689	$61.67	$61.65	$61.70
Purchase #2	$128.48	3.733%	$133.2762	$133.28	$133.30	$133.30
Purchase #3	$31.86	5.601%	$33.6445	$33.64	$33.65	$33.60
Purchase #4	$236.95	13.725%	$269.4714	$269.47	$269.45	$269.50
Purchase #5	$36.59	12.302%	$41.0913	$41.09	$41.10	$41.10
Purchase #6	$118.38	12.124%	$132.7324	$132.73	$132.75	$132.70
Purchase #7	$118.61	10.739%	$131.3475	$131.35	$131.35	$131.30
7 purchase totals =	$729.22		$803.2322	$803.23	$803.25	$803.20