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	$205.60	10.701%	$227.6013	$227.60	$227.60	$227.60
Purchase #2	$94.67	9.309%	$103.4828	$103.48	$103.50	$103.50
Purchase #3	$162.42	6.326%	$172.6947	$172.69	$172.70	$172.70
Purchase #4	$45.98	5.440%	$48.4813	$48.48	$48.50	$48.50
Purchase #5	$7.72	4.749%	$8.0866	$8.09	$8.10	$8.10
Purchase #6	$42.48	6.703%	$45.3274	$45.33	$45.35	$45.30
Purchase #7	$77.59	7.576%	$83.4682	$83.47	$83.45	$83.50
7 purchase totals =	$636.46		$689.1423	$689.14	$689.20	$689.20