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	$161.65	11.731%	$180.6132	$180.61	$180.60	$180.60
Purchase #2	$32.36	4.212%	$33.723	$33.72	$33.70	$33.70
Purchase #3	$74.33	8.455%	$80.6146	$80.61	$80.60	$80.60
Purchase #4	$73.86	12.149%	$82.8333	$82.83	$82.85	$82.80
Purchase #5	$148.41	13.754%	$168.8223	$168.82	$168.80	$168.80
Purchase #6	$18.84	4.588%	$19.7044	$19.70	$19.70	$19.70
Purchase #7	$209.59	10.526%	$231.6514	$231.65	$231.65	$231.70
7 purchase totals =	$719.04		$797.9622	$797.94	$797.90	$797.90