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	$32.35	10.350%	$35.6982	$35.70	$35.70	$35.70
Purchase #2	$126.38	13.392%	$143.3048	$143.30	$143.30	$143.30
Purchase #3	$42.78	11.623%	$47.7523	$47.75	$47.75	$47.80
Purchase #4	$50.59	5.673%	$53.46	$53.46	$53.45	$53.50
Purchase #5	$123.94	7.247%	$132.9219	$132.92	$132.90	$132.90
Purchase #6	$213.59	3.518%	$221.1041	$221.10	$221.10	$221.10
Purchase #7	$208.71	6.461%	$222.1948	$222.19	$222.20	$222.20
7 purchase totals =	$798.34		$856.4361	$856.42	$856.40	$856.50