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	$72.35	8.389%	$78.4194	$78.42	$78.40	$78.40
Purchase #2	$115.39	10.750%	$127.7944	$127.79	$127.80	$127.80
Purchase #3	$147.48	5.845%	$156.1002	$156.10	$156.10	$156.10
Purchase #4	$151.94	6.263%	$161.456	$161.46	$161.45	$161.50
Purchase #5	$89.90	8.267%	$97.332	$97.33	$97.35	$97.30
Purchase #6	$76.46	6.758%	$81.6272	$81.63	$81.65	$81.60
Purchase #7	$233.71	4.760%	$244.8346	$244.83	$244.85	$244.80
7 purchase totals =	$887.23		$947.5638	$947.56	$947.60	$947.50