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	$46.52	11.599%	$51.9159	$51.92	$51.90	$51.90
Purchase #2	$96.41	4.407%	$100.6588	$100.66	$100.65	$100.70
Purchase #3	$41.99	5.838%	$44.4414	$44.44	$44.45	$44.40
Purchase #4	$92.97	9.116%	$101.4451	$101.45	$101.45	$101.40
Purchase #5	$152.70	10.486%	$168.7121	$168.71	$168.70	$168.70
Purchase #6	$243.81	10.399%	$269.1638	$269.16	$269.15	$269.20
Purchase #7	$75.94	3.550%	$78.6359	$78.64	$78.65	$78.60
7 purchase totals =	$750.34		$814.9730	$814.98	$814.95	$814.90