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	$104.72	6.435%	$111.4587	$111.46	$111.45	$111.50
Purchase #2	$77.78	10.794%	$86.1756	$86.18	$86.20	$86.20
Purchase #3	$74.77	6.294%	$79.476	$79.48	$79.50	$79.50
Purchase #4	$109.81	12.753%	$123.8141	$123.81	$123.80	$123.80
Purchase #5	$187.44	9.470%	$205.1906	$205.19	$205.20	$205.20
Purchase #6	$183.61	12.377%	$206.3354	$206.34	$206.35	$206.30
Purchase #7	$210.99	4.663%	$220.8285	$220.83	$220.85	$220.80
7 purchase totals =	$949.12		$1,033.2789	$1,033.29	$1,033.35	$1,033.30