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	$134.30	5.576%	$141.7886	$141.79	$141.80	$141.80
Purchase #2	$8.30	9.523%	$9.0904	$9.09	$9.10	$9.10
Purchase #3	$73.86	4.645%	$77.2908	$77.29	$77.30	$77.30
Purchase #4	$191.69	12.105%	$214.8941	$214.89	$214.90	$214.90
Purchase #5	$95.94	10.730%	$106.2344	$106.23	$106.25	$106.20
Purchase #6	$51.96	7.453%	$55.8326	$55.83	$55.85	$55.80
Purchase #7	$56.49	10.523%	$62.4344	$62.43	$62.45	$62.40
7 purchase totals =	$612.54		$667.5653	$667.55	$667.65	$667.50