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	$117.57	8.210%	$127.2225	$127.22	$127.20	$127.20
Purchase #2	$209.65	6.397%	$223.0613	$223.06	$223.05	$223.10
Purchase #3	$140.80	8.234%	$152.3935	$152.39	$152.40	$152.40
Purchase #4	$149.26	4.314%	$155.6991	$155.70	$155.70	$155.70
Purchase #5	$131.84	9.574%	$144.4624	$144.46	$144.45	$144.50
Purchase #6	$223.58	6.166%	$237.3659	$237.37	$237.35	$237.40
Purchase #7	$108.71	4.515%	$113.6183	$113.62	$113.60	$113.60
7 purchase totals =	$1,081.41		$1,153.8230	$1,153.82	$1,153.75	$1,153.90