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	$66.95	12.570%	$75.3656	$75.37	$75.35	$75.40
Purchase #2	$206.52	13.199%	$233.7786	$233.78	$233.80	$233.80
Purchase #3	$204.94	3.325%	$211.7543	$211.75	$211.75	$211.80
Purchase #4	$31.84	3.204%	$32.8602	$32.86	$32.85	$32.90
Purchase #5	$77.64	10.523%	$85.8101	$85.81	$85.80	$85.80
Purchase #6	$205.42	6.766%	$219.3187	$219.32	$219.30	$219.30
Purchase #7	$74.85	11.566%	$83.5072	$83.51	$83.50	$83.50
7 purchase totals =	$868.16		$942.3947	$942.40	$942.35	$942.50