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	$101.51	3.323%	$104.8832	$104.88	$104.90	$104.90
Purchase #2	$81.59	10.653%	$90.2818	$90.28	$90.30	$90.30
Purchase #3	$183.84	6.395%	$195.5966	$195.60	$195.60	$195.60
Purchase #4	$54.49	9.700%	$59.7755	$59.78	$59.80	$59.80
Purchase #5	$184.74	4.126%	$192.3624	$192.36	$192.35	$192.40
Purchase #6	$195.47	10.728%	$216.44	$216.44	$216.45	$216.40
Purchase #7	$65.85	6.615%	$70.206	$70.21	$70.20	$70.20
7 purchase totals =	$867.49		$929.5455	$929.55	$929.60	$929.60