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	$185.54	13.509%	$210.6046	$210.60	$210.60	$210.60
Purchase #2	$84.74	12.799%	$95.5859	$95.59	$95.60	$95.60
Purchase #3	$12.29	9.251%	$13.4269	$13.43	$13.45	$13.40
Purchase #4	$117.78	13.149%	$133.2669	$133.27	$133.25	$133.30
Purchase #5	$150.33	3.356%	$155.3751	$155.38	$155.40	$155.40
Purchase #6	$134.83	3.535%	$139.5962	$139.60	$139.60	$139.60
Purchase #7	$35.53	3.118%	$36.6378	$36.64	$36.65	$36.60
7 purchase totals =	$721.04		$784.4934	$784.51	$784.55	$784.50