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	$93.40	3.196%	$96.3851	$96.39	$96.40	$96.40
Purchase #2	$83.31	7.373%	$89.4524	$89.45	$89.45	$89.50
Purchase #3	$103.86	12.745%	$117.097	$117.10	$117.10	$117.10
Purchase #4	$122.51	8.453%	$132.8658	$132.87	$132.85	$132.90
Purchase #5	$222.33	5.824%	$235.2785	$235.28	$235.30	$235.30
Purchase #6	$244.89	4.252%	$255.3027	$255.30	$255.30	$255.30
Purchase #7	$7.65	11.663%	$8.5422	$8.54	$8.55	$8.50
7 purchase totals =	$877.95		$934.9237	$934.93	$934.95	$935.00