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	$11.60	7.437%	$12.4627	$12.46	$12.45	$12.50
Purchase #2	$56.68	7.675%	$61.0302	$61.03	$61.05	$61.00
Purchase #3	$81.87	4.483%	$85.5402	$85.54	$85.55	$85.50
Purchase #4	$238.88	7.435%	$256.6407	$256.64	$256.65	$256.60
Purchase #5	$200.35	4.795%	$209.9568	$209.96	$209.95	$210.00
Purchase #6	$39.58	9.637%	$43.3943	$43.39	$43.40	$43.40
Purchase #7	$28.87	5.361%	$30.4177	$30.42	$30.40	$30.40
7 purchase totals =	$657.83		$699.4426	$699.44	$699.45	$699.40