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	$87.58	3.491%	$90.6374	$90.64	$90.65	$90.60
Purchase #2	$6.40	13.155%	$7.2419	$7.24	$7.25	$7.20
Purchase #3	$135.56	5.116%	$142.4952	$142.50	$142.50	$142.50
Purchase #4	$65.74	6.820%	$70.2235	$70.22	$70.20	$70.20
Purchase #5	$163.34	9.668%	$179.1317	$179.13	$179.15	$179.10
Purchase #6	$139.75	10.613%	$154.5817	$154.58	$154.60	$154.60
Purchase #7	$42.32	3.590%	$43.8393	$43.84	$43.85	$43.80
7 purchase totals =	$640.69		$688.1507	$688.15	$688.20	$688.00