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	$250.47	5.585%	$264.4587	$264.46	$264.45	$264.50
Purchase #2	$154.91	3.212%	$159.8857	$159.89	$159.90	$159.90
Purchase #3	$71.72	3.679%	$74.3586	$74.36	$74.35	$74.40
Purchase #4	$122.83	11.856%	$137.3927	$137.39	$137.40	$137.40
Purchase #5	$226.61	5.330%	$238.6883	$238.69	$238.70	$238.70
Purchase #6	$168.40	13.567%	$191.2468	$191.25	$191.25	$191.20
Purchase #7	$74.59	12.675%	$84.0443	$84.04	$84.05	$84.00
7 purchase totals =	$1,069.53		$1,150.0751	$1,150.08	$1,150.10	$1,150.10