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	$172.78	3.536%	$178.8895	$178.89	$178.90	$178.90
Purchase #2	$211.39	4.185%	$220.2367	$220.24	$220.25	$220.20
Purchase #3	$52.50	3.145%	$54.1511	$54.15	$54.15	$54.20
Purchase #4	$194.75	6.118%	$206.6648	$206.66	$206.65	$206.70
Purchase #5	$35.79	4.553%	$37.4195	$37.42	$37.40	$37.40
Purchase #6	$109.84	9.451%	$120.221	$120.22	$120.20	$120.20
Purchase #7	$164.82	11.391%	$183.5946	$183.59	$183.60	$183.60
7 purchase totals =	$941.87		$1,001.1772	$1,001.17	$1,001.15	$1,001.20