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	$100.59	3.836%	$104.4486	$104.45	$104.45	$104.40
Purchase #2	$20.85	5.808%	$22.061	$22.06	$22.05	$22.10
Purchase #3	$240.89	7.540%	$259.0531	$259.05	$259.05	$259.10
Purchase #4	$187.27	13.382%	$212.3305	$212.33	$212.35	$212.30
Purchase #5	$100.63	8.850%	$109.5358	$109.54	$109.55	$109.50
Purchase #6	$111.56	11.503%	$124.3927	$124.39	$124.40	$124.40
Purchase #7	$190.69	3.351%	$197.08	$197.08	$197.10	$197.10
7 purchase totals =	$952.48		$1,028.9017	$1,028.90	$1,028.95	$1,028.90