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	$41.89	9.279%	$45.777	$45.78	$45.80	$45.80
Purchase #2	$75.63	10.856%	$83.8404	$83.84	$83.85	$83.80
Purchase #3	$121.46	5.429%	$128.0541	$128.05	$128.05	$128.10
Purchase #4	$169.42	12.495%	$190.589	$190.59	$190.60	$190.60
Purchase #5	$210.48	9.127%	$229.6905	$229.69	$229.70	$229.70
Purchase #6	$70.59	3.112%	$72.7868	$72.79	$72.80	$72.80
Purchase #7	$153.46	13.389%	$174.0068	$174.01	$174.00	$174.00
7 purchase totals =	$842.93		$924.7446	$924.75	$924.80	$924.80