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	$156.38	7.135%	$167.5377	$167.54	$167.55	$167.50
Purchase #2	$122.75	7.279%	$131.685	$131.69	$131.70	$131.70
Purchase #3	$16.87	9.583%	$18.4867	$18.49	$18.50	$18.50
Purchase #4	$132.91	11.431%	$148.1029	$148.10	$148.10	$148.10
Purchase #5	$71.53	4.381%	$74.6637	$74.66	$74.65	$74.70
Purchase #6	$115.86	13.554%	$131.5637	$131.56	$131.55	$131.60
Purchase #7	$236.63	8.331%	$256.3436	$256.34	$256.35	$256.30
7 purchase totals =	$852.93		$928.3833	$928.38	$928.40	$928.40