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	$43.64	5.404%	$45.9983	$46.00	$46.00	$46.00
Purchase #2	$173.87	9.281%	$190.0069	$190.01	$190.00	$190.00
Purchase #3	$116.48	13.185%	$131.8379	$131.84	$131.85	$131.80
Purchase #4	$142.73	11.568%	$159.241	$159.24	$159.25	$159.20
Purchase #5	$39.59	9.127%	$43.2034	$43.20	$43.20	$43.20
Purchase #6	$249.51	5.261%	$262.6367	$262.64	$262.65	$262.60
Purchase #7	$69.76	3.409%	$72.1381	$72.14	$72.15	$72.10
7 purchase totals =	$835.58		$905.0623	$905.07	$905.10	$904.90