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	$138.97	3.361%	$143.6408	$143.64	$143.65	$143.60
Purchase #2	$207.60	12.788%	$234.1479	$234.15	$234.15	$234.10
Purchase #3	$131.53	3.804%	$136.5334	$136.53	$136.55	$136.50
Purchase #4	$89.58	12.789%	$101.0364	$101.04	$101.05	$101.00
Purchase #5	$243.78	11.704%	$272.312	$272.31	$272.30	$272.30
Purchase #6	$249.83	13.713%	$284.0892	$284.09	$284.10	$284.10
Purchase #7	$227.54	12.212%	$255.3272	$255.33	$255.35	$255.30
7 purchase totals =	$1,288.83		$1,427.0869	$1,427.09	$1,427.15	$1,426.90