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	$51.93	7.601%	$55.8772	$55.88	$55.90	$55.90
Purchase #2	$225.39	13.451%	$255.7072	$255.71	$255.70	$255.70
Purchase #3	$212.60	11.439%	$236.9193	$236.92	$236.90	$236.90
Purchase #4	$52.27	9.290%	$57.1259	$57.13	$57.15	$57.10
Purchase #5	$158.41	5.525%	$167.1622	$167.16	$167.15	$167.20
Purchase #6	$201.68	13.729%	$229.3686	$229.37	$229.35	$229.40
Purchase #7	$105.50	4.223%	$109.9553	$109.96	$109.95	$110.00
7 purchase totals =	$1,007.78		$1,112.1157	$1,112.13	$1,112.10	$1,112.20