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	$140.46	3.130%	$144.8564	$144.86	$144.85	$144.90
Purchase #2	$78.44	3.504%	$81.1885	$81.19	$81.20	$81.20
Purchase #3	$83.35	5.321%	$87.7851	$87.79	$87.80	$87.80
Purchase #4	$36.89	8.655%	$40.0828	$40.08	$40.10	$40.10
Purchase #5	$164.77	4.172%	$171.6442	$171.64	$171.65	$171.60
Purchase #6	$210.69	6.857%	$225.137	$225.14	$225.15	$225.10
Purchase #7	$46.51	4.356%	$48.536	$48.54	$48.55	$48.50
7 purchase totals =	$761.11		$799.2300	$799.24	$799.30	$799.20