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	$118.81	11.399%	$132.3532	$132.35	$132.35	$132.40
Purchase #2	$216.29	6.129%	$229.5464	$229.55	$229.55	$229.50
Purchase #3	$108.42	4.707%	$113.5233	$113.52	$113.50	$113.50
Purchase #4	$39.27	12.230%	$44.0727	$44.07	$44.05	$44.10
Purchase #5	$84.33	6.339%	$89.6757	$89.68	$89.70	$89.70
Purchase #6	$33.89	10.295%	$37.379	$37.38	$37.40	$37.40
Purchase #7	$145.56	12.671%	$164.0039	$164.00	$164.00	$164.00
7 purchase totals =	$746.57		$810.5542	$810.55	$810.55	$810.60