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	$162.61	7.364%	$174.5846	$174.58	$174.60	$174.60
Purchase #2	$11.48	10.277%	$12.6598	$12.66	$12.65	$12.70
Purchase #3	$220.89	4.718%	$231.3116	$231.31	$231.30	$231.30
Purchase #4	$176.51	13.497%	$200.3336	$200.33	$200.35	$200.30
Purchase #5	$234.44	13.836%	$266.8771	$266.88	$266.90	$266.90
Purchase #6	$21.99	4.109%	$22.8936	$22.89	$22.90	$22.90
Purchase #7	$196.82	13.203%	$222.8061	$222.81	$222.80	$222.80
7 purchase totals =	$1,024.74		$1,131.4664	$1,131.46	$1,131.50	$1,131.50