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	$166.73	10.377%	$184.0316	$184.03	$184.05	$184.00
Purchase #2	$67.63	4.356%	$70.576	$70.58	$70.60	$70.60
Purchase #3	$104.59	12.641%	$117.8112	$117.81	$117.80	$117.80
Purchase #4	$11.92	10.107%	$13.1248	$13.12	$13.10	$13.10
Purchase #5	$7.64	3.572%	$7.9129	$7.91	$7.90	$7.90
Purchase #6	$94.59	10.106%	$104.1493	$104.15	$104.15	$104.10
Purchase #7	$43.89	11.386%	$48.8873	$48.89	$48.90	$48.90
7 purchase totals =	$496.99		$546.4931	$546.49	$546.50	$546.40