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	$37.33	13.192%	$42.2546	$42.25	$42.25	$42.30
Purchase #2	$32.94	4.120%	$34.2971	$34.30	$34.30	$34.30
Purchase #3	$235.88	8.255%	$255.3519	$255.35	$255.35	$255.40
Purchase #4	$105.65	6.152%	$112.1496	$112.15	$112.15	$112.10
Purchase #5	$196.33	11.513%	$218.9335	$218.93	$218.95	$218.90
Purchase #6	$231.99	5.613%	$245.0116	$245.01	$245.00	$245.00
Purchase #7	$170.52	11.193%	$189.6063	$189.61	$189.60	$189.60
7 purchase totals =	$1,010.64		$1,097.6046	$1,097.60	$1,097.60	$1,097.60