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	$169.94	11.154%	$188.8951	$188.90	$188.90	$188.90
Purchase #2	$111.72	8.266%	$120.9548	$120.95	$120.95	$121.00
Purchase #3	$166.71	8.751%	$181.2988	$181.30	$181.30	$181.30
Purchase #4	$40.90	12.272%	$45.9192	$45.92	$45.90	$45.90
Purchase #5	$175.46	10.357%	$193.6324	$193.63	$193.65	$193.60
Purchase #6	$96.42	13.635%	$109.5669	$109.57	$109.55	$109.60
Purchase #7	$158.66	4.177%	$165.2872	$165.29	$165.30	$165.30
7 purchase totals =	$919.81		$1,005.5544	$1,005.56	$1,005.55	$1,005.60