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	$24.34	4.546%	$25.4465	$25.45	$25.45	$25.40
Purchase #2	$62.42	13.299%	$70.7212	$70.72	$70.70	$70.70
Purchase #3	$162.99	6.575%	$173.7066	$173.71	$173.70	$173.70
Purchase #4	$148.68	12.518%	$167.2918	$167.29	$167.30	$167.30
Purchase #5	$100.52	11.315%	$111.8938	$111.89	$111.90	$111.90
Purchase #6	$201.54	9.164%	$220.0091	$220.01	$220.00	$220.00
Purchase #7	$171.33	5.551%	$180.8405	$180.84	$180.85	$180.80
7 purchase totals =	$871.82		$949.9095	$949.91	$949.90	$949.80