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	$129.90	7.694%	$139.8945	$139.89	$139.90	$139.90
Purchase #2	$61.32	5.334%	$64.5908	$64.59	$64.60	$64.60
Purchase #3	$59.55	3.457%	$61.6086	$61.61	$61.60	$61.60
Purchase #4	$55.68	12.822%	$62.8193	$62.82	$62.80	$62.80
Purchase #5	$134.83	10.568%	$149.0788	$149.08	$149.10	$149.10
Purchase #6	$55.72	3.355%	$57.5894	$57.59	$57.60	$57.60
Purchase #7	$105.67	11.156%	$117.4585	$117.46	$117.45	$117.50
7 purchase totals =	$602.67		$653.0399	$653.04	$653.05	$653.10