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	$250.91	4.604%	$262.4619	$262.46	$262.45	$262.50
Purchase #2	$98.27	6.706%	$104.86	$104.86	$104.85	$104.90
Purchase #3	$40.96	3.778%	$42.5075	$42.51	$42.50	$42.50
Purchase #4	$177.60	8.339%	$192.4101	$192.41	$192.40	$192.40
Purchase #5	$168.76	11.417%	$188.0273	$188.03	$188.05	$188.00
Purchase #6	$57.50	5.685%	$60.7689	$60.77	$60.75	$60.80
Purchase #7	$23.78	6.478%	$25.3205	$25.32	$25.30	$25.30
7 purchase totals =	$817.78		$876.3562	$876.36	$876.30	$876.40