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	$163.59	4.181%	$170.4297	$170.43	$170.45	$170.40
Purchase #2	$70.54	10.282%	$77.7929	$77.79	$77.80	$77.80
Purchase #3	$60.50	5.581%	$63.8765	$63.88	$63.90	$63.90
Purchase #4	$6.71	10.367%	$7.4056	$7.41	$7.40	$7.40
Purchase #5	$83.67	7.246%	$89.7327	$89.73	$89.75	$89.70
Purchase #6	$134.43	3.859%	$139.6177	$139.62	$139.60	$139.60
Purchase #7	$219.71	6.262%	$233.4682	$233.47	$233.45	$233.50
7 purchase totals =	$739.15		$782.3233	$782.33	$782.35	$782.30