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	$141.36	6.645%	$150.7534	$150.75	$150.75	$150.80
Purchase #2	$192.55	3.295%	$198.8945	$198.89	$198.90	$198.90
Purchase #3	$32.41	6.511%	$34.5202	$34.52	$34.50	$34.50
Purchase #4	$45.89	5.374%	$48.3561	$48.36	$48.35	$48.40
Purchase #5	$122.31	13.326%	$138.609	$138.61	$138.60	$138.60
Purchase #6	$224.34	13.713%	$255.1037	$255.10	$255.10	$255.10
Purchase #7	$210.97	8.577%	$229.0649	$229.06	$229.05	$229.10
7 purchase totals =	$969.83		$1,055.3018	$1,055.29	$1,055.25	$1,055.40