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	$144.72	6.372%	$153.9416	$153.94	$153.95	$153.90
Purchase #2	$186.54	5.471%	$196.7456	$196.75	$196.75	$196.70
Purchase #3	$219.80	13.528%	$249.5345	$249.53	$249.55	$249.50
Purchase #4	$64.99	11.631%	$72.549	$72.55	$72.55	$72.50
Purchase #5	$159.77	7.846%	$172.3056	$172.31	$172.30	$172.30
Purchase #6	$38.59	8.639%	$41.9238	$41.92	$41.90	$41.90
Purchase #7	$48.60	7.696%	$52.3403	$52.34	$52.35	$52.30
7 purchase totals =	$863.01		$939.3404	$939.34	$939.35	$939.10