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	$207.58	5.302%	$218.5859	$218.59	$218.60	$218.60
Purchase #2	$10.38	10.422%	$11.4618	$11.46	$11.45	$11.50
Purchase #3	$69.97	12.269%	$78.5546	$78.55	$78.55	$78.60
Purchase #4	$243.69	6.588%	$259.7443	$259.74	$259.75	$259.70
Purchase #5	$37.78	11.862%	$42.2615	$42.26	$42.25	$42.30
Purchase #6	$165.27	9.106%	$180.3195	$180.32	$180.30	$180.30
Purchase #7	$35.45	7.792%	$38.2123	$38.21	$38.20	$38.20
7 purchase totals =	$770.12		$829.1399	$829.13	$829.10	$829.20