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	$89.44	13.874%	$101.8489	$101.85	$101.85	$101.80
Purchase #2	$95.48	10.468%	$105.4748	$105.47	$105.45	$105.50
Purchase #3	$153.30	6.103%	$162.6559	$162.66	$162.65	$162.70
Purchase #4	$144.64	10.487%	$159.8084	$159.81	$159.80	$159.80
Purchase #5	$101.32	3.172%	$104.5339	$104.53	$104.55	$104.50
Purchase #6	$112.69	9.844%	$123.7832	$123.78	$123.80	$123.80
Purchase #7	$28.75	12.462%	$32.3328	$32.33	$32.35	$32.30
7 purchase totals =	$725.62		$790.4379	$790.43	$790.45	$790.40