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	$95.25	3.435%	$98.5218	$98.52	$98.50	$98.50
Purchase #2	$125.52	13.558%	$142.538	$142.54	$142.55	$142.50
Purchase #3	$107.27	7.431%	$115.2412	$115.24	$115.25	$115.20
Purchase #4	$238.93	4.574%	$249.8587	$249.86	$249.85	$249.90
Purchase #5	$97.35	6.105%	$103.2932	$103.29	$103.30	$103.30
Purchase #6	$149.98	5.197%	$157.7745	$157.77	$157.75	$157.80
Purchase #7	$139.31	8.540%	$151.2071	$151.21	$151.20	$151.20
7 purchase totals =	$953.61		$1,018.4345	$1,018.43	$1,018.40	$1,018.40