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	$57.47	4.235%	$59.9039	$59.90	$59.90	$59.90
Purchase #2	$178.51	10.143%	$196.6163	$196.62	$196.60	$196.60
Purchase #3	$123.53	6.807%	$131.9387	$131.94	$131.95	$131.90
Purchase #4	$177.93	13.601%	$202.1303	$202.13	$202.15	$202.10
Purchase #5	$230.97	11.761%	$258.1344	$258.13	$258.15	$258.10
Purchase #6	$203.60	9.478%	$222.8972	$222.90	$222.90	$222.90
Purchase #7	$82.32	13.270%	$93.2439	$93.24	$93.25	$93.20
7 purchase totals =	$1,054.33		$1,164.8647	$1,164.86	$1,164.90	$1,164.70