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	$139.31	6.318%	$148.1116	$148.11	$148.10	$148.10
Purchase #2	$241.35	7.789%	$260.1488	$260.15	$260.15	$260.10
Purchase #3	$167.59	13.685%	$190.5247	$190.52	$190.50	$190.50
Purchase #4	$189.56	4.716%	$198.4996	$198.50	$198.50	$198.50
Purchase #5	$110.39	10.412%	$121.8838	$121.88	$121.90	$121.90
Purchase #6	$32.72	13.554%	$37.1549	$37.15	$37.15	$37.20
Purchase #7	$66.83	3.264%	$69.0113	$69.01	$69.00	$69.00
7 purchase totals =	$947.75		$1,025.3347	$1,025.32	$1,025.30	$1,025.30