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	$24.71	3.853%	$25.6621	$25.66	$25.65	$25.70
Purchase #2	$54.33	9.855%	$59.6842	$59.68	$59.70	$59.70
Purchase #3	$100.47	11.599%	$112.1235	$112.12	$112.10	$112.10
Purchase #4	$200.97	7.294%	$215.6288	$215.63	$215.65	$215.60
Purchase #5	$181.32	8.481%	$196.6977	$196.70	$196.70	$196.70
Purchase #6	$140.79	9.390%	$154.0102	$154.01	$154.00	$154.00
Purchase #7	$152.78	11.192%	$169.8791	$169.88	$169.90	$169.90
7 purchase totals =	$855.37		$933.6856	$933.68	$933.70	$933.70