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	$190.59	5.139%	$200.3844	$200.38	$200.40	$200.40
Purchase #2	$59.27	3.354%	$61.2579	$61.26	$61.25	$61.30
Purchase #3	$106.60	9.262%	$116.4733	$116.47	$116.45	$116.50
Purchase #4	$199.51	5.298%	$210.08	$210.08	$210.10	$210.10
Purchase #5	$191.32	11.392%	$213.1152	$213.12	$213.10	$213.10
Purchase #6	$187.89	8.304%	$203.4924	$203.49	$203.50	$203.50
Purchase #7	$205.53	8.571%	$223.146	$223.15	$223.15	$223.10
7 purchase totals =	$1,140.71		$1,227.9492	$1,227.95	$1,227.95	$1,228.00