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	$47.76	9.506%	$52.3001	$52.30	$52.30	$52.30
Purchase #2	$56.32	10.789%	$62.3964	$62.40	$62.40	$62.40
Purchase #3	$213.38	11.651%	$238.2409	$238.24	$238.25	$238.20
Purchase #4	$20.63	4.442%	$21.5464	$21.55	$21.55	$21.50
Purchase #5	$86.39	9.146%	$94.2912	$94.29	$94.30	$94.30
Purchase #6	$58.47	7.136%	$62.6424	$62.64	$62.65	$62.60
Purchase #7	$115.55	7.831%	$124.5987	$124.60	$124.60	$124.60
7 purchase totals =	$598.50		$656.0161	$656.02	$656.05	$655.90