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	$221.46	6.839%	$236.6056	$236.61	$236.60	$236.60
Purchase #2	$11.85	13.475%	$13.4468	$13.45	$13.45	$13.40
Purchase #3	$173.44	11.260%	$192.9693	$192.97	$192.95	$193.00
Purchase #4	$85.85	4.540%	$89.7476	$89.75	$89.75	$89.70
Purchase #5	$133.69	8.740%	$145.3745	$145.37	$145.35	$145.40
Purchase #6	$120.83	5.435%	$127.3971	$127.40	$127.40	$127.40
Purchase #7	$245.74	4.616%	$257.0834	$257.08	$257.10	$257.10
7 purchase totals =	$992.86		$1,062.6243	$1,062.63	$1,062.60	$1,062.60