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	$161.75	5.662%	$170.9083	$170.91	$170.90	$170.90
Purchase #2	$143.56	12.422%	$161.393	$161.39	$161.40	$161.40
Purchase #3	$136.61	3.656%	$141.6045	$141.60	$141.60	$141.60
Purchase #4	$250.50	10.405%	$276.5645	$276.56	$276.55	$276.60
Purchase #5	$87.80	9.786%	$96.3921	$96.39	$96.40	$96.40
Purchase #6	$33.51	5.835%	$35.4653	$35.47	$35.45	$35.50
Purchase #7	$133.33	13.653%	$151.5335	$151.53	$151.55	$151.50
7 purchase totals =	$947.06		$1,033.8612	$1,033.85	$1,033.85	$1,033.90