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	$44.39	7.434%	$47.69	$47.69	$47.70	$47.70
Purchase #2	$244.30	5.801%	$258.4718	$258.47	$258.45	$258.50
Purchase #3	$231.86	9.126%	$253.0195	$253.02	$253.00	$253.00
Purchase #4	$176.46	8.228%	$190.9791	$190.98	$191.00	$191.00
Purchase #5	$116.28	13.293%	$131.7371	$131.74	$131.75	$131.70
Purchase #6	$78.54	12.791%	$88.5861	$88.59	$88.60	$88.60
Purchase #7	$188.73	13.844%	$214.8578	$214.86	$214.85	$214.90
7 purchase totals =	$1,080.56		$1,185.3414	$1,185.35	$1,185.35	$1,185.40