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	$181.64	5.517%	$191.6611	$191.66	$191.65	$191.70
Purchase #2	$226.70	9.839%	$249.005	$249.01	$249.00	$249.00
Purchase #3	$123.31	6.556%	$131.3942	$131.39	$131.40	$131.40
Purchase #4	$95.41	10.563%	$105.4882	$105.49	$105.50	$105.50
Purchase #5	$206.73	6.650%	$220.4775	$220.48	$220.50	$220.50
Purchase #6	$218.58	5.195%	$229.9352	$229.94	$229.95	$229.90
Purchase #7	$134.68	4.867%	$141.2349	$141.23	$141.25	$141.20
7 purchase totals =	$1,187.05		$1,269.1961	$1,269.20	$1,269.25	$1,269.20