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	$39.82	13.152%	$45.0571	$45.06	$45.05	$45.10
Purchase #2	$197.30	6.256%	$209.6431	$209.64	$209.65	$209.60
Purchase #3	$244.26	6.189%	$259.3773	$259.38	$259.40	$259.40
Purchase #4	$129.33	10.253%	$142.5902	$142.59	$142.60	$142.60
Purchase #5	$38.94	9.206%	$42.5248	$42.52	$42.50	$42.50
Purchase #6	$79.56	8.106%	$86.0091	$86.01	$86.00	$86.00
Purchase #7	$224.95	8.659%	$244.4284	$244.43	$244.45	$244.40
7 purchase totals =	$954.16		$1,029.6300	$1,029.63	$1,029.65	$1,029.60