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	$37.84	13.845%	$43.0789	$43.08	$43.10	$43.10
Purchase #2	$99.65	7.494%	$107.1178	$107.12	$107.10	$107.10
Purchase #3	$9.69	13.488%	$10.997	$11.00	$11.00	$11.00
Purchase #4	$125.34	13.409%	$142.1468	$142.15	$142.15	$142.10
Purchase #5	$40.47	11.348%	$45.0625	$45.06	$45.05	$45.10
Purchase #6	$93.37	11.704%	$104.298	$104.30	$104.30	$104.30
Purchase #7	$113.48	8.596%	$123.2347	$123.23	$123.25	$123.20
7 purchase totals =	$519.84		$575.9357	$575.94	$575.95	$575.90