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	$236.73	10.167%	$260.7983	$260.80	$260.80	$260.80
Purchase #2	$118.62	10.864%	$131.5069	$131.51	$131.50	$131.50
Purchase #3	$54.99	8.400%	$59.6092	$59.61	$59.60	$59.60
Purchase #4	$70.77	11.441%	$78.8668	$78.87	$78.85	$78.90
Purchase #5	$173.89	3.671%	$180.2735	$180.27	$180.25	$180.30
Purchase #6	$117.89	11.767%	$131.7621	$131.76	$131.75	$131.80
Purchase #7	$129.96	10.398%	$143.4732	$143.47	$143.45	$143.50
7 purchase totals =	$902.85		$986.2900	$986.29	$986.20	$986.40