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	$173.51	4.693%	$181.6528	$181.65	$181.65	$181.70
Purchase #2	$44.55	11.439%	$49.6461	$49.65	$49.65	$49.60
Purchase #3	$55.54	4.143%	$57.841	$57.84	$57.85	$57.80
Purchase #4	$72.61	12.303%	$81.5432	$81.54	$81.55	$81.50
Purchase #5	$85.52	6.858%	$91.385	$91.39	$91.40	$91.40
Purchase #6	$87.60	3.410%	$90.5872	$90.59	$90.60	$90.60
Purchase #7	$226.49	10.501%	$250.2737	$250.27	$250.25	$250.30
7 purchase totals =	$745.82		$802.9290	$802.93	$802.95	$802.90