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	$61.31	8.512%	$66.5287	$66.53	$66.55	$66.50
Purchase #2	$198.83	7.397%	$213.5375	$213.54	$213.55	$213.50
Purchase #3	$224.97	11.550%	$250.954	$250.95	$250.95	$251.00
Purchase #4	$31.63	4.728%	$33.1255	$33.13	$33.15	$33.10
Purchase #5	$149.30	7.508%	$160.5094	$160.51	$160.50	$160.50
Purchase #6	$92.46	8.366%	$100.1952	$100.20	$100.20	$100.20
Purchase #7	$182.85	4.831%	$191.6835	$191.68	$191.70	$191.70
7 purchase totals =	$941.35		$1,016.5338	$1,016.54	$1,016.60	$1,016.50