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	$199.92	8.827%	$217.5669	$217.57	$217.55	$217.60
Purchase #2	$72.74	6.410%	$77.4026	$77.40	$77.40	$77.40
Purchase #3	$78.72	4.306%	$82.1097	$82.11	$82.10	$82.10
Purchase #4	$80.25	5.192%	$84.4166	$84.42	$84.40	$84.40
Purchase #5	$103.82	5.684%	$109.7211	$109.72	$109.70	$109.70
Purchase #6	$185.67	4.425%	$193.8859	$193.89	$193.90	$193.90
Purchase #7	$67.59	7.413%	$72.6004	$72.60	$72.60	$72.60
7 purchase totals =	$788.71		$837.7032	$837.71	$837.65	$837.70