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	$95.72	10.846%	$106.1018	$106.10	$106.10	$106.10
Purchase #2	$40.85	9.795%	$44.8513	$44.85	$44.85	$44.90
Purchase #3	$115.47	8.443%	$125.2191	$125.22	$125.20	$125.20
Purchase #4	$124.91	13.127%	$141.3069	$141.31	$141.30	$141.30
Purchase #5	$137.67	3.476%	$142.4554	$142.46	$142.45	$142.50
Purchase #6	$59.47	9.780%	$65.2862	$65.29	$65.30	$65.30
Purchase #7	$167.80	13.597%	$190.6158	$190.62	$190.60	$190.60
7 purchase totals =	$741.89		$815.8365	$815.85	$815.80	$815.90