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	$96.72	8.392%	$104.8367	$104.84	$104.85	$104.80
Purchase #2	$200.80	8.858%	$218.5869	$218.59	$218.60	$218.60
Purchase #3	$166.36	8.851%	$181.0845	$181.08	$181.10	$181.10
Purchase #4	$168.78	11.143%	$187.5872	$187.59	$187.60	$187.60
Purchase #5	$128.56	8.600%	$139.6162	$139.62	$139.60	$139.60
Purchase #6	$178.93	3.828%	$185.7794	$185.78	$185.80	$185.80
Purchase #7	$80.51	10.185%	$88.7099	$88.71	$88.70	$88.70
7 purchase totals =	$1,020.66		$1,106.2008	$1,106.21	$1,106.25	$1,106.20