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	$33.49	12.175%	$37.5674	$37.57	$37.55	$37.60
Purchase #2	$133.65	5.218%	$140.6239	$140.62	$140.60	$140.60
Purchase #3	$146.88	10.545%	$162.3685	$162.37	$162.35	$162.40
Purchase #4	$132.78	13.533%	$150.7491	$150.75	$150.75	$150.70
Purchase #5	$233.65	5.561%	$246.6433	$246.64	$246.65	$246.60
Purchase #6	$173.90	10.312%	$191.8326	$191.83	$191.85	$191.80
Purchase #7	$98.61	13.659%	$112.0791	$112.08	$112.10	$112.10
7 purchase totals =	$952.96		$1,041.8639	$1,041.86	$1,041.85	$1,041.80