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	$104.39	7.270%	$111.9792	$111.98	$112.00	$112.00
Purchase #2	$227.56	3.772%	$236.1436	$236.14	$236.15	$236.10
Purchase #3	$107.93	8.827%	$117.457	$117.46	$117.45	$117.50
Purchase #4	$192.39	8.534%	$208.8086	$208.81	$208.80	$208.80
Purchase #5	$139.71	8.524%	$151.6189	$151.62	$151.60	$151.60
Purchase #6	$163.34	12.580%	$183.8882	$183.89	$183.90	$183.90
Purchase #7	$127.72	3.266%	$131.8913	$131.89	$131.90	$131.90
7 purchase totals =	$1,063.04		$1,141.7868	$1,141.79	$1,141.80	$1,141.80