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	$47.40	13.142%	$53.6293	$53.63	$53.65	$53.60
Purchase #2	$91.71	9.414%	$100.3436	$100.34	$100.35	$100.30
Purchase #3	$152.61	8.364%	$165.3743	$165.37	$165.35	$165.40
Purchase #4	$109.34	5.726%	$115.6008	$115.60	$115.60	$115.60
Purchase #5	$173.94	7.752%	$187.4238	$187.42	$187.40	$187.40
Purchase #6	$162.54	5.731%	$171.8552	$171.86	$171.85	$171.90
Purchase #7	$110.36	6.803%	$117.8678	$117.87	$117.85	$117.90
7 purchase totals =	$847.90		$912.0948	$912.09	$912.05	$912.10