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	$35.88	3.542%	$37.1509	$37.15	$37.15	$37.20
Purchase #2	$204.84	9.346%	$223.9843	$223.98	$224.00	$224.00
Purchase #3	$179.91	5.762%	$190.2764	$190.28	$190.30	$190.30
Purchase #4	$71.45	12.379%	$80.2948	$80.29	$80.30	$80.30
Purchase #5	$76.88	13.619%	$87.3503	$87.35	$87.35	$87.40
Purchase #6	$167.72	6.396%	$178.4474	$178.45	$178.45	$178.40
Purchase #7	$156.46	4.118%	$162.903	$162.90	$162.90	$162.90
7 purchase totals =	$893.14		$960.4071	$960.40	$960.45	$960.50