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	$204.43	9.792%	$224.4478	$224.45	$224.45	$224.40
Purchase #2	$78.84	12.128%	$88.4017	$88.40	$88.40	$88.40
Purchase #3	$182.59	11.412%	$203.4272	$203.43	$203.45	$203.40
Purchase #4	$156.51	11.490%	$174.493	$174.49	$174.50	$174.50
Purchase #5	$187.56	10.147%	$206.5917	$206.59	$206.60	$206.60
Purchase #6	$49.34	8.638%	$53.602	$53.60	$53.60	$53.60
Purchase #7	$82.89	4.329%	$86.4783	$86.48	$86.50	$86.50
7 purchase totals =	$942.16		$1,037.4417	$1,037.44	$1,037.50	$1,037.40