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	$230.87	6.476%	$245.8211	$245.82	$245.80	$245.80
Purchase #2	$116.98	11.667%	$130.6281	$130.63	$130.65	$130.60
Purchase #3	$37.57	12.534%	$42.279	$42.28	$42.30	$42.30
Purchase #4	$40.65	5.416%	$42.8516	$42.85	$42.85	$42.90
Purchase #5	$178.36	5.205%	$187.6436	$187.64	$187.65	$187.60
Purchase #6	$101.40	9.525%	$111.0584	$111.06	$111.05	$111.10
Purchase #7	$96.61	6.139%	$102.5409	$102.54	$102.55	$102.50
7 purchase totals =	$802.44		$862.8227	$862.82	$862.85	$862.80