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	$201.54	11.333%	$224.3805	$224.38	$224.40	$224.40
Purchase #2	$160.35	4.277%	$167.2082	$167.21	$167.20	$167.20
Purchase #3	$190.82	3.177%	$196.8824	$196.88	$196.90	$196.90
Purchase #4	$179.97	9.356%	$196.808	$196.81	$196.80	$196.80
Purchase #5	$211.83	10.535%	$234.1463	$234.15	$234.15	$234.10
Purchase #6	$163.92	5.437%	$172.8323	$172.83	$172.85	$172.80
Purchase #7	$43.86	6.315%	$46.6298	$46.63	$46.65	$46.60
7 purchase totals =	$1,152.29		$1,238.8875	$1,238.89	$1,238.95	$1,238.80