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	$93.35	7.814%	$100.6444	$100.64	$100.65	$100.60
Purchase #2	$114.69	12.493%	$129.0182	$129.02	$129.00	$129.00
Purchase #3	$198.61	3.424%	$205.4104	$205.41	$205.40	$205.40
Purchase #4	$105.57	3.500%	$109.265	$109.27	$109.25	$109.30
Purchase #5	$75.83	3.734%	$78.6615	$78.66	$78.65	$78.70
Purchase #6	$184.61	13.536%	$209.5988	$209.60	$209.60	$209.60
Purchase #7	$40.67	10.365%	$44.8854	$44.89	$44.90	$44.90
7 purchase totals =	$813.33		$877.4837	$877.49	$877.45	$877.50