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	$113.69	5.273%	$119.6849	$119.68	$119.70	$119.70
Purchase #2	$224.86	3.626%	$233.0134	$233.01	$233.00	$233.00
Purchase #3	$43.72	13.106%	$49.4499	$49.45	$49.45	$49.40
Purchase #4	$122.56	6.729%	$130.8071	$130.81	$130.80	$130.80
Purchase #5	$207.33	12.623%	$233.5013	$233.50	$233.50	$233.50
Purchase #6	$247.44	7.144%	$265.1171	$265.12	$265.10	$265.10
Purchase #7	$37.77	11.589%	$42.1472	$42.15	$42.15	$42.10
7 purchase totals =	$997.37		$1,073.7209	$1,073.72	$1,073.70	$1,073.60