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	$144.38	10.368%	$159.3493	$159.35	$159.35	$159.30
Purchase #2	$85.61	4.729%	$89.6585	$89.66	$89.65	$89.70
Purchase #3	$142.80	5.295%	$150.3613	$150.36	$150.35	$150.40
Purchase #4	$123.30	12.171%	$138.3068	$138.31	$138.30	$138.30
Purchase #5	$173.77	7.414%	$186.6533	$186.65	$186.65	$186.70
Purchase #6	$51.58	5.460%	$54.3963	$54.40	$54.40	$54.40
Purchase #7	$94.81	12.444%	$106.6082	$106.61	$106.60	$106.60
7 purchase totals =	$816.25		$885.3337	$885.34	$885.30	$885.40