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	$220.67	7.161%	$236.4722	$236.47	$236.45	$236.50
Purchase #2	$222.82	13.855%	$253.6917	$253.69	$253.70	$253.70
Purchase #3	$74.77	5.363%	$78.7799	$78.78	$78.80	$78.80
Purchase #4	$95.85	10.300%	$105.7226	$105.72	$105.70	$105.70
Purchase #5	$248.87	13.140%	$281.5715	$281.57	$281.55	$281.60
Purchase #6	$26.93	7.125%	$28.8488	$28.85	$28.85	$28.80
Purchase #7	$115.95	6.501%	$123.4879	$123.49	$123.50	$123.50
7 purchase totals =	$1,005.86		$1,108.5746	$1,108.57	$1,108.55	$1,108.60