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	$118.87	5.609%	$125.5374	$125.54	$125.55	$125.50
Purchase #2	$131.72	6.694%	$140.5373	$140.54	$140.55	$140.50
Purchase #3	$158.75	4.659%	$166.1462	$166.15	$166.15	$166.10
Purchase #4	$100.41	6.475%	$106.9115	$106.91	$106.90	$106.90
Purchase #5	$40.87	6.534%	$43.5404	$43.54	$43.55	$43.50
Purchase #6	$90.60	4.259%	$94.4587	$94.46	$94.45	$94.50
Purchase #7	$73.45	10.356%	$81.0565	$81.06	$81.05	$81.10
7 purchase totals =	$714.67		$758.1880	$758.20	$758.20	$758.10