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	$168.39	11.233%	$187.3052	$187.31	$187.30	$187.30
Purchase #2	$100.35	11.479%	$111.8692	$111.87	$111.85	$111.90
Purchase #3	$49.60	6.114%	$52.6325	$52.63	$52.65	$52.60
Purchase #4	$53.55	10.823%	$59.3457	$59.35	$59.35	$59.30
Purchase #5	$46.70	6.618%	$49.7906	$49.79	$49.80	$49.80
Purchase #6	$14.50	13.305%	$16.4292	$16.43	$16.45	$16.40
Purchase #7	$190.34	4.780%	$199.4383	$199.44	$199.45	$199.40
7 purchase totals =	$623.43		$676.8107	$676.82	$676.85	$676.70