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	$189.42	5.513%	$199.8627	$199.86	$199.85	$199.90
Purchase #2	$186.38	10.420%	$205.8008	$205.80	$205.80	$205.80
Purchase #3	$45.89	12.544%	$51.6464	$51.65	$51.65	$51.60
Purchase #4	$87.83	7.652%	$94.5508	$94.55	$94.55	$94.60
Purchase #5	$189.55	11.225%	$210.827	$210.83	$210.85	$210.80
Purchase #6	$80.56	10.545%	$89.0551	$89.06	$89.05	$89.10
Purchase #7	$195.67	11.818%	$218.7943	$218.79	$218.80	$218.80
7 purchase totals =	$975.30		$1,070.5371	$1,070.54	$1,070.55	$1,070.60