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	$153.34	13.564%	$174.139	$174.14	$174.15	$174.10
Purchase #2	$236.59	5.298%	$249.1245	$249.12	$249.10	$249.10
Purchase #3	$102.85	8.127%	$111.2086	$111.21	$111.20	$111.20
Purchase #4	$75.27	3.504%	$77.9075	$77.91	$77.90	$77.90
Purchase #5	$64.87	11.521%	$72.3437	$72.34	$72.35	$72.30
Purchase #6	$107.79	7.489%	$115.8624	$115.86	$115.85	$115.90
Purchase #7	$18.80	6.837%	$20.0854	$20.09	$20.10	$20.10
7 purchase totals =	$759.51		$820.6711	$820.67	$820.65	$820.60