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	$137.38	11.838%	$153.643	$153.64	$153.65	$153.60
Purchase #2	$61.39	11.102%	$68.2055	$68.21	$68.20	$68.20
Purchase #3	$111.96	10.305%	$123.4975	$123.50	$123.50	$123.50
Purchase #4	$35.43	10.773%	$39.2469	$39.25	$39.25	$39.20
Purchase #5	$151.34	12.267%	$169.9049	$169.90	$169.90	$169.90
Purchase #6	$121.31	12.457%	$136.4216	$136.42	$136.40	$136.40
Purchase #7	$87.69	10.241%	$96.6703	$96.67	$96.65	$96.70
7 purchase totals =	$706.50		$787.5897	$787.59	$787.55	$787.50