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	$77.28	10.661%	$85.5188	$85.52	$85.50	$85.50
Purchase #2	$86.68	9.815%	$95.1876	$95.19	$95.20	$95.20
Purchase #3	$142.42	9.837%	$156.4299	$156.43	$156.45	$156.40
Purchase #4	$143.61	3.552%	$148.711	$148.71	$148.70	$148.70
Purchase #5	$215.81	12.733%	$243.2891	$243.29	$243.30	$243.30
Purchase #6	$22.90	11.541%	$25.5429	$25.54	$25.55	$25.50
Purchase #7	$128.75	6.868%	$137.5926	$137.59	$137.60	$137.60
7 purchase totals =	$817.45		$892.2719	$892.27	$892.30	$892.20