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	$159.28	8.146%	$172.2549	$172.25	$172.25	$172.30
Purchase #2	$186.95	5.312%	$196.8808	$196.88	$196.90	$196.90
Purchase #3	$189.36	13.645%	$215.1982	$215.20	$215.20	$215.20
Purchase #4	$232.29	11.266%	$258.4598	$258.46	$258.45	$258.50
Purchase #5	$46.32	6.590%	$49.3725	$49.37	$49.35	$49.40
Purchase #6	$107.57	5.518%	$113.5057	$113.51	$113.50	$113.50
Purchase #7	$195.60	4.771%	$204.9321	$204.93	$204.95	$204.90
7 purchase totals =	$1,117.37		$1,210.6040	$1,210.60	$1,210.60	$1,210.70