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	$110.31	3.678%	$114.3672	$114.37	$114.35	$114.40
Purchase #2	$14.67	7.329%	$15.7452	$15.75	$15.75	$15.70
Purchase #3	$102.55	6.732%	$109.4537	$109.45	$109.45	$109.50
Purchase #4	$134.53	10.283%	$148.3637	$148.36	$148.35	$148.40
Purchase #5	$90.56	5.336%	$95.3923	$95.39	$95.40	$95.40
Purchase #6	$70.55	4.111%	$73.4503	$73.45	$73.45	$73.50
Purchase #7	$113.79	8.309%	$123.2448	$123.24	$123.25	$123.20
7 purchase totals =	$636.96		$680.0172	$680.01	$680.00	$680.10