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	$96.31	11.215%	$107.1112	$107.11	$107.10	$107.10
Purchase #2	$67.74	7.440%	$72.7799	$72.78	$72.80	$72.80
Purchase #3	$122.92	6.523%	$130.9381	$130.94	$130.95	$130.90
Purchase #4	$99.54	13.241%	$112.7201	$112.72	$112.70	$112.70
Purchase #5	$94.86	9.732%	$104.0918	$104.09	$104.10	$104.10
Purchase #6	$182.50	5.525%	$192.5831	$192.58	$192.60	$192.60
Purchase #7	$143.96	3.267%	$148.6632	$148.66	$148.65	$148.70
7 purchase totals =	$807.83		$868.8874	$868.88	$868.90	$868.90