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	$102.31	4.246%	$106.6541	$106.65	$106.65	$106.70
Purchase #2	$5.33	11.558%	$5.946	$5.95	$5.95	$5.90
Purchase #3	$91.53	9.152%	$99.9068	$99.91	$99.90	$99.90
Purchase #4	$247.74	7.341%	$265.9266	$265.93	$265.95	$265.90
Purchase #5	$240.86	11.804%	$269.2911	$269.29	$269.30	$269.30
Purchase #6	$114.78	7.706%	$123.6249	$123.62	$123.60	$123.60
Purchase #7	$117.32	8.653%	$127.4717	$127.47	$127.45	$127.50
7 purchase totals =	$919.87		$998.8212	$998.82	$998.80	$998.80