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	$151.83	10.705%	$168.0834	$168.08	$168.10	$168.10
Purchase #2	$29.54	7.848%	$31.8583	$31.86	$31.85	$31.90
Purchase #3	$112.98	8.792%	$122.9132	$122.91	$122.90	$122.90
Purchase #4	$41.73	4.271%	$43.5123	$43.51	$43.50	$43.50
Purchase #5	$85.83	8.425%	$93.0612	$93.06	$93.05	$93.10
Purchase #6	$94.26	11.470%	$105.0716	$105.07	$105.05	$105.10
Purchase #7	$198.78	5.407%	$209.528	$209.53	$209.55	$209.50
7 purchase totals =	$714.95		$774.0280	$774.02	$774.00	$774.10