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	$230.83	6.597%	$246.0579	$246.06	$246.05	$246.10
Purchase #2	$71.49	13.199%	$80.926	$80.93	$80.95	$80.90
Purchase #3	$12.58	13.816%	$14.3181	$14.32	$14.30	$14.30
Purchase #4	$190.93	12.149%	$214.1261	$214.13	$214.15	$214.10
Purchase #5	$148.36	13.621%	$168.5681	$168.57	$168.55	$168.60
Purchase #6	$238.76	3.159%	$246.3024	$246.30	$246.30	$246.30
Purchase #7	$196.83	9.525%	$215.5781	$215.58	$215.60	$215.60
7 purchase totals =	$1,089.78		$1,185.8767	$1,185.89	$1,185.90	$1,185.90