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	$145.50	11.512%	$162.25	$162.25	$162.25	$162.30
Purchase #2	$37.85	11.680%	$42.2709	$42.27	$42.25	$42.30
Purchase #3	$128.47	11.537%	$143.2916	$143.29	$143.30	$143.30
Purchase #4	$46.58	10.732%	$51.579	$51.58	$51.60	$51.60
Purchase #5	$222.41	4.691%	$232.8433	$232.84	$232.85	$232.80
Purchase #6	$137.31	9.331%	$150.1224	$150.12	$150.10	$150.10
Purchase #7	$250.77	3.665%	$259.9607	$259.96	$259.95	$260.00
7 purchase totals =	$968.89		$1,042.3179	$1,042.31	$1,042.30	$1,042.40