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	$214.50	13.818%	$244.1396	$244.14	$244.15	$244.10
Purchase #2	$84.97	5.463%	$89.6119	$89.61	$89.60	$89.60
Purchase #3	$96.76	7.323%	$103.8457	$103.85	$103.85	$103.80
Purchase #4	$58.79	9.697%	$64.4909	$64.49	$64.50	$64.50
Purchase #5	$162.38	4.787%	$170.1531	$170.15	$170.15	$170.20
Purchase #6	$96.72	5.618%	$102.1537	$102.15	$102.15	$102.20
Purchase #7	$168.74	12.203%	$189.3313	$189.33	$189.35	$189.30
7 purchase totals =	$882.86		$963.7262	$963.72	$963.75	$963.70