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	$80.54	10.425%	$88.9363	$88.94	$88.95	$88.90
Purchase #2	$199.54	4.753%	$209.0241	$209.02	$209.00	$209.00
Purchase #3	$16.85	4.715%	$17.6445	$17.64	$17.65	$17.60
Purchase #4	$45.93	13.758%	$52.249	$52.25	$52.25	$52.20
Purchase #5	$35.25	12.314%	$39.5907	$39.59	$39.60	$39.60
Purchase #6	$143.93	13.125%	$162.8208	$162.82	$162.80	$162.80
Purchase #7	$163.86	13.211%	$185.5075	$185.51	$185.50	$185.50
7 purchase totals =	$685.90		$755.7729	$755.77	$755.75	$755.60