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	$85.96	9.130%	$93.8081	$93.81	$93.80	$93.80
Purchase #2	$247.54	7.794%	$266.8333	$266.83	$266.85	$266.80
Purchase #3	$143.88	12.866%	$162.3916	$162.39	$162.40	$162.40
Purchase #4	$172.88	3.145%	$178.3171	$178.32	$178.30	$178.30
Purchase #5	$36.74	10.766%	$40.6954	$40.70	$40.70	$40.70
Purchase #6	$92.81	9.360%	$101.497	$101.50	$101.50	$101.50
Purchase #7	$242.77	4.389%	$253.4252	$253.43	$253.45	$253.40
7 purchase totals =	$1,022.58		$1,096.9677	$1,096.98	$1,097.00	$1,096.90