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	$180.65	6.235%	$191.9135	$191.91	$191.90	$191.90
Purchase #2	$120.67	8.108%	$130.4539	$130.45	$130.45	$130.50
Purchase #3	$236.79	6.716%	$252.6928	$252.69	$252.70	$252.70
Purchase #4	$198.38	9.539%	$217.3035	$217.30	$217.30	$217.30
Purchase #5	$62.86	5.726%	$66.4594	$66.46	$66.45	$66.50
Purchase #6	$95.59	5.559%	$100.9038	$100.90	$100.90	$100.90
Purchase #7	$109.65	7.433%	$117.8003	$117.80	$117.80	$117.80
7 purchase totals =	$1,004.59		$1,077.5272	$1,077.51	$1,077.50	$1,077.60