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	$195.27	9.142%	$213.1216	$213.12	$213.10	$213.10
Purchase #2	$215.47	4.384%	$224.9162	$224.92	$224.90	$224.90
Purchase #3	$100.84	4.837%	$105.7176	$105.72	$105.70	$105.70
Purchase #4	$72.41	8.432%	$78.5156	$78.52	$78.50	$78.50
Purchase #5	$152.85	9.205%	$166.9198	$166.92	$166.90	$166.90
Purchase #6	$151.93	8.412%	$164.7104	$164.71	$164.70	$164.70
Purchase #7	$12.38	10.267%	$13.6511	$13.65	$13.65	$13.70
7 purchase totals =	$901.15		$967.5523	$967.56	$967.45	$967.50