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	$196.92	12.506%	$221.5468	$221.55	$221.55	$221.50
Purchase #2	$70.69	10.400%	$78.0418	$78.04	$78.05	$78.00
Purchase #3	$38.74	6.739%	$41.3507	$41.35	$41.35	$41.40
Purchase #4	$98.59	12.178%	$110.5963	$110.60	$110.60	$110.60
Purchase #5	$207.85	8.534%	$225.5879	$225.59	$225.60	$225.60
Purchase #6	$78.29	4.626%	$81.9117	$81.91	$81.90	$81.90
Purchase #7	$177.97	12.709%	$200.5882	$200.59	$200.60	$200.60
7 purchase totals =	$869.05		$959.6234	$959.63	$959.65	$959.60