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	$243.47	7.404%	$261.4965	$261.50	$261.50	$261.50
Purchase #2	$234.40	4.280%	$244.4323	$244.43	$244.45	$244.40
Purchase #3	$70.67	10.384%	$78.0084	$78.01	$78.00	$78.00
Purchase #4	$232.77	3.738%	$241.4709	$241.47	$241.45	$241.50
Purchase #5	$163.66	13.125%	$185.1404	$185.14	$185.15	$185.10
Purchase #6	$37.84	7.745%	$40.7707	$40.77	$40.75	$40.80
Purchase #7	$70.44	7.337%	$75.6082	$75.61	$75.60	$75.60
7 purchase totals =	$1,053.25		$1,126.9274	$1,126.93	$1,126.90	$1,126.90