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	$128.75	10.819%	$142.6795	$142.68	$142.70	$142.70
Purchase #2	$236.73	9.446%	$259.0915	$259.09	$259.10	$259.10
Purchase #3	$199.41	9.314%	$217.983	$217.98	$218.00	$218.00
Purchase #4	$37.74	5.280%	$39.7327	$39.73	$39.75	$39.70
Purchase #5	$141.63	7.266%	$151.9208	$151.92	$151.90	$151.90
Purchase #6	$183.39	4.577%	$191.7838	$191.78	$191.80	$191.80
Purchase #7	$150.85	12.342%	$169.4679	$169.47	$169.45	$169.50
7 purchase totals =	$1,078.50		$1,172.6592	$1,172.65	$1,172.70	$1,172.70