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	$128.82	3.126%	$132.8469	$132.85	$132.85	$132.80
Purchase #2	$27.93	4.256%	$29.1187	$29.12	$29.10	$29.10
Purchase #3	$109.46	12.706%	$123.368	$123.37	$123.35	$123.40
Purchase #4	$69.94	8.459%	$75.8562	$75.86	$75.85	$75.90
Purchase #5	$42.29	13.125%	$47.8406	$47.84	$47.85	$47.80
Purchase #6	$167.47	3.183%	$172.8006	$172.80	$172.80	$172.80
Purchase #7	$68.98	5.162%	$72.5407	$72.54	$72.55	$72.50
7 purchase totals =	$614.89		$654.3717	$654.38	$654.35	$654.30