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	$101.98	3.596%	$105.6472	$105.65	$105.65	$105.60
Purchase #2	$57.74	5.668%	$61.0127	$61.01	$61.00	$61.00
Purchase #3	$112.53	3.226%	$116.1602	$116.16	$116.15	$116.20
Purchase #4	$98.61	8.350%	$106.8439	$106.84	$106.85	$106.80
Purchase #5	$107.61	9.142%	$117.4477	$117.45	$117.45	$117.40
Purchase #6	$110.40	6.516%	$117.5937	$117.59	$117.60	$117.60
Purchase #7	$127.58	3.111%	$131.549	$131.55	$131.55	$131.50
7 purchase totals =	$716.45		$756.2544	$756.25	$756.25	$756.10