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	$162.87	5.502%	$171.8311	$171.83	$171.85	$171.80
Purchase #2	$64.81	3.855%	$67.3084	$67.31	$67.30	$67.30
Purchase #3	$99.29	5.542%	$104.7927	$104.79	$104.80	$104.80
Purchase #4	$17.49	4.372%	$18.2547	$18.25	$18.25	$18.30
Purchase #5	$106.57	10.219%	$117.4604	$117.46	$117.45	$117.50
Purchase #6	$229.39	3.222%	$236.7809	$236.78	$236.80	$236.80
Purchase #7	$238.97	11.723%	$266.9845	$266.98	$267.00	$267.00
7 purchase totals =	$919.39		$983.4127	$983.40	$983.45	$983.50