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	$95.30	3.696%	$98.8223	$98.82	$98.80	$98.80
Purchase #2	$146.81	11.862%	$164.2246	$164.22	$164.20	$164.20
Purchase #3	$170.80	5.185%	$179.656	$179.66	$179.65	$179.70
Purchase #4	$143.49	5.609%	$151.5384	$151.54	$151.55	$151.50
Purchase #5	$190.48	11.755%	$212.8709	$212.87	$212.85	$212.90
Purchase #6	$241.46	8.181%	$261.2138	$261.21	$261.20	$261.20
Purchase #7	$127.72	9.478%	$139.8253	$139.83	$139.85	$139.80
7 purchase totals =	$1,116.06		$1,208.1513	$1,208.15	$1,208.10	$1,208.10