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	$55.25	7.739%	$59.5258	$59.53	$59.55	$59.50
Purchase #2	$190.76	8.839%	$207.6213	$207.62	$207.60	$207.60
Purchase #3	$197.39	4.129%	$205.5402	$205.54	$205.55	$205.50
Purchase #4	$130.33	8.654%	$141.6088	$141.61	$141.60	$141.60
Purchase #5	$19.30	13.457%	$21.8972	$21.90	$21.90	$21.90
Purchase #6	$16.95	3.780%	$17.5907	$17.59	$17.60	$17.60
Purchase #7	$60.51	7.836%	$65.2516	$65.25	$65.25	$65.30
7 purchase totals =	$670.49		$719.0356	$719.04	$719.05	$719.00