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	$36.47	5.133%	$38.342	$38.34	$38.35	$38.30
Purchase #2	$41.60	3.673%	$43.128	$43.13	$43.15	$43.10
Purchase #3	$197.41	13.179%	$223.4267	$223.43	$223.45	$223.40
Purchase #4	$142.32	10.198%	$156.8338	$156.83	$156.85	$156.80
Purchase #5	$9.72	5.340%	$10.239	$10.24	$10.25	$10.20
Purchase #6	$96.46	9.663%	$105.7809	$105.78	$105.80	$105.80
Purchase #7	$151.63	13.732%	$172.4518	$172.45	$172.45	$172.50
7 purchase totals =	$675.61		$750.2022	$750.20	$750.30	$750.10