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	$144.72	12.382%	$162.6392	$162.64	$162.65	$162.60
Purchase #2	$232.27	6.171%	$246.6034	$246.60	$246.60	$246.60
Purchase #3	$78.98	8.540%	$85.7249	$85.72	$85.70	$85.70
Purchase #4	$117.66	10.254%	$129.7249	$129.72	$129.70	$129.70
Purchase #5	$176.44	3.624%	$182.8342	$182.83	$182.85	$182.80
Purchase #6	$83.62	7.434%	$89.8363	$89.84	$89.85	$89.80
Purchase #7	$54.32	5.873%	$57.5102	$57.51	$57.50	$57.50
7 purchase totals =	$888.01		$954.8731	$954.86	$954.85	$954.70