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	$182.43	12.523%	$205.2757	$205.28	$205.30	$205.30
Purchase #2	$171.48	4.245%	$178.7593	$178.76	$178.75	$178.80
Purchase #3	$238.25	13.701%	$270.8926	$270.89	$270.90	$270.90
Purchase #4	$71.29	10.712%	$78.9266	$78.93	$78.95	$78.90
Purchase #5	$89.50	9.263%	$97.7904	$97.79	$97.80	$97.80
Purchase #6	$166.51	3.656%	$172.5976	$172.60	$172.60	$172.60
Purchase #7	$143.43	9.132%	$156.528	$156.53	$156.55	$156.50
7 purchase totals =	$1,062.89		$1,160.7702	$1,160.78	$1,160.85	$1,160.80