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	$134.43	7.817%	$144.9384	$144.94	$144.95	$144.90
Purchase #2	$90.72	4.391%	$94.7035	$94.70	$94.70	$94.70
Purchase #3	$169.27	5.476%	$178.5392	$178.54	$178.55	$178.50
Purchase #4	$191.27	4.113%	$199.1369	$199.14	$199.15	$199.10
Purchase #5	$24.56	5.259%	$25.8516	$25.85	$25.85	$25.90
Purchase #6	$50.71	11.621%	$56.603	$56.60	$56.60	$56.60
Purchase #7	$239.77	6.342%	$254.9762	$254.98	$255.00	$255.00
7 purchase totals =	$900.73		$954.7488	$954.75	$954.80	$954.70