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	$84.59	7.242%	$90.716	$90.72	$90.70	$90.70
Purchase #2	$217.67	9.262%	$237.8306	$237.83	$237.85	$237.80
Purchase #3	$208.52	8.253%	$225.7292	$225.73	$225.75	$225.70
Purchase #4	$163.89	13.265%	$185.63	$185.63	$185.65	$185.60
Purchase #5	$126.27	12.762%	$142.3846	$142.38	$142.40	$142.40
Purchase #6	$116.86	11.548%	$130.355	$130.36	$130.35	$130.40
Purchase #7	$140.33	6.135%	$148.9392	$148.94	$148.95	$148.90
7 purchase totals =	$1,058.13		$1,161.5846	$1,161.59	$1,161.65	$1,161.50