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	$204.85	10.484%	$226.3265	$226.33	$226.35	$226.30
Purchase #2	$112.27	9.636%	$123.0883	$123.09	$123.10	$123.10
Purchase #3	$101.58	3.589%	$105.2257	$105.23	$105.25	$105.20
Purchase #4	$37.93	5.126%	$39.8743	$39.87	$39.85	$39.90
Purchase #5	$198.56	10.443%	$219.2956	$219.30	$219.30	$219.30
Purchase #6	$234.93	12.684%	$264.7285	$264.73	$264.75	$264.70
Purchase #7	$37.47	6.257%	$39.8145	$39.81	$39.80	$39.80
7 purchase totals =	$927.59		$1,018.3534	$1,018.36	$1,018.40	$1,018.30